NOVELTY - For a solid electrolyte, an organosilicon polymer comprising specific structure unit with inorganic backbone-chain structure and organic side-chain structure is used.    USE - In solid electrolyte which is used in solid-state lithium-ion battery (claimed).    ADVANTAGE - The organosilicon polymer is a polymer compound comprising, both inorganic backbone-chain structure and organic side-chain structure, and has the characteristics of both organic polymer and inorganic polymer as well as many unique properties. Thus the solid electrolyte formed by the organosilicon polymer and its solid-state lithium-ion battery have many good characteristics including a good lithium-ion-conduction capability, better resistance to high temperatures, wider range of operating temperatures, and better thermal stability. As compared to carbon-skeleton polymers such as polyesters or polyethers, the organosilicon polymer has better thermal endurance, wider range of operating temperatures, better film-forming performance and better thermostability. Thus the solid electrolyte and the solid-state lithium-ion battery formed by the organosilicon polymer has, higher ionic conductivity, higher energy density, better thermal endurance, better stability and security.    DETAILED DESCRIPTION - For a solid electrolyte, an organosilicon polymer comprising at least one structure unit of formula (I) or (II) is used.    R1,R2=substituting groups which are respectively selected from alkyl, alkoxy, polyether group and terminal group with -Y1A structure;    R'x=alkyl or aryl;    n=greater than 1;    Y1=anion;    A=cation.    At least one of the substituting groups R1 and R2 is the terminal group with the -Y1A structure. INDEPENDENT CLAIMS are included for the following:    (1) a solid electrolyte, comprising the organosilicon polymer;    (2) a solid-state lithium-ion battery, comprising a cathode which comprises a cathode active material, an anode which comprises an anode active material, and the solid electrolyte; and    (3) preparation of the polymer involving: reaction of a silicon-containing polymeric monomer B, a polymeric monomer C and alkoxide in a solvent.