NOVELTY - A multilayer crosslinked doped fluorine-containing ionic membrane contains a fluorine-containing ion-exchange resin and has layers. At least one layer of membrane comprises an imine-containing compound (I) having crosslinked net structure. An inorganic dopant having water-retaining property or proton exchange property is added to at least one layer of membrane. At least one layer of membrane is microporous reinforced membrane. The multilayer crosslinked doped fluorine-containing ionic membrane has conductivity of 40-150 mS/cm and tensile strength of 10-60 MPa.    USE - Multilayer crosslinked doped fluorine-containing ionic membrane is used for producing fuel cell.    ADVANTAGE - The multilayer crosslinked doped fluorine-containing ionic membrane has excellent mechanical strength, dimensional stability, ion exchange capacity and conductivity.    DETAILED DESCRIPTION - A multilayer crosslinked doped fluorine-containing ionic membrane contains a fluorine-containing ion-exchange resin with equivalent weight of 600-1300, and has 2-40 layers and total thickness of 10-300 microns. At least one layer of membrane comprises an imine-containing compound of formula (I) having crosslinked net structure. An inorganic dopant having water-retaining property or proton exchange property is added to at least one layer of membrane. At least one layer of membrane is microporous reinforced membrane. The multilayer crosslinked doped fluorine-containing ionic membrane has conductivity of 40-150 mS/cm and tensile strength of 10-60 MPa. The mass ratio of inorganic dopant and fluorine-containing ion-exchange resin is 0.1-100:100. The fluorine-containing ion-exchange resin is obtained by copolymerizing a fluorine-containing olefin, one or more fluorine-containing alkene monomers having a functional group, and one or more fluorine-containing alkene monomers having crosslinked structure, or mixture of copolymer. The fluorine-containing olefin is chosen from tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene or vinylidene fluoride. The fluorine-containing alkene monomer having functional group is chosen from alkene compound of formula: Y1(CF2)a(CF2R1)b(CFR2)cO(C(-CF2X)FCF2O)m-CF=CF2 (II), R3CF=CF(CF2)dY2 (III) and F2C=CFOCF2C(-CF2OCF3)FOCF2CF2Y3 (IV). The fluorine-containing alkene monomer having crosslinked structure is chosen from alkene compound of formula: F2C=CFR9Y4 (V) and Y5(CF2)q(CF2R10)r(CFR11)sO(C(-CF2X)FCF2O)m-CF=CF2 (VI).    R=methylene or perfluoromethylene;    n=0-10;    a-c=0-1, all are not 0;    m,q-s=0 or 1, all of q, r and s are not 0;    X=fluoro, chloro, bromo or iodo;    d=0-5;    R1-R3=fluorine-containing alkyl or chlorofluorocarbyl;    Y1-Y3=SO2M, COOR4 or PO(OR5)(OR6);    M=Br, F, Cl, OR' or NR7R8;    R',R4-R6=H, methyl, ethyl, propyl, sodium, lithium, potassium or ammonium;    Y4,Y5=chloro, bromo, iodo or cyano;    R9-R11=fluorine-containing alkyl;and    R7,R8=H, methyl, ethyl or propyl.    An INDEPENDENT CLAIM is included for preparation of multilayer crosslinked doped fluorine-containing ion membrane, which involves preparing layer of reinforced multilayer crosslinked fluorine-containing ion-exchange membrane or forming membrane compounded with microporous membrane with a solution or melted substance containing fluorine-containing ion-exchange resin and inorganic dopant by casting, extrusion, hot pressing, spin coating, curtain coating, screen printing, spray coating or dipping process, and preparing multilayer membrane by compounding single-layer membrane, preparing multilayer membrane with solution or melted substance on the single-layer membrane, preparing multilayer membrane by casting, extrusion, hot pressing, spin coating, curtain coating, screen printing, spray coating or dipping, or preparing multilayer membrane by compounding multilayer membrane and single-layer membrane or multilayer membrane and multilayer membrane. A crosslinking agent and/or initiator is added during preparation of layer of microporous membrane and preparation of multilayer membrane, or crosslinking agent and/or initiator is dispersed in a solvent and the membrane at swelling mode is immersed in the solvent. The membrane is treated to form crosslinked structure by reacting sulfuryl fluoride, sulfonyl chloride or sulfonyl bromide-type resin with ammonia, hydrazine, organic diamine or substance which releases ammonia, hydrazine and organic diamine after chemical treatment. The organic diamine is 1-10C alkyl or diamine halothane. The substance which releases ammonia, hydrazine and organic diamine after chemical treatment includes ammonia, hydrazine or organic or inorganic acid salt of organic diamine, urea or guanidine. The obtained product is treated by alkali liquor and acid liquor.