NOVELTY - A multi-pore alloy film with polyvinylidene fluoride is prepared by melting polyvinylidene fluoride and polymethylmethacrylate, diluting agent or cosolvent and additive into melting machine one after another and cooling in air to obtain granules; adding the prepared raw material of the blend into double screw extruder to form melting blend; after pressing, passing the melting blend through filter and spinning pump in turn to form hollow nascent fiber; and airing the melting blend after cooling and washing.    USE - Method of preparing multi-pore alloy film with polyvinylidene fluoride for treating and recycling wastewater (claimed), particularly for membrane bioreactor.    ADVANTAGE - The hollow nascent fiber micro-pore membrane of multi-pore alloy film with polyvinylidene fluoride has good chemical resistance, hydrophilicity, high intensity, large flux, strong toughness and uniformly distributed pores with good pollution resistance.    DETAILED DESCRIPTION - Preparation of multi-pore alloy film with polyvinylidene fluoride comprises:    (A) preparation of blend raw material by placing polyvinylidene fluoride P1 and polymethylmethacrylate P2, diluting agent or cosolvent S, and additive A into melting machine one after another to melt at 160-200 degrees C and cooling in air to obtain granules; where P2/P1=0-0.25 (preferably 0.05-0.10), (P1+P2)/(P1+P2+S)=25-55 (preferably 30-40)wt.%, and A/(P1+P2)=0-0.20 (preferably 0.05-0.12);    (B) extrusion molding a hollow fiber by adding the raw material of the blend into double screw extruder at 4 kg/hour to form melting blend, in which the extruder is heated in eight areas in the direction of screw length, the temperature for 1-8 areas are 120-220 degrees C in turn, and the rotating speed of the screw is 120 t/m; passing the melting blend through filter and spinning pump in turn, and then pressing out of hollow fiber ring-shaped finish mold to form hollow nascent fiber, in which the external diameter of the ring-shaped finish mold is 4.5 mm, the internal diameter is 4 mm, and the pressure of the nitrogen in ring-shaped finish mold center is the water column of 30-60 mm; lowering the temperature of the nascent fiber to 5-20 degrees C, in which the distance from the exit of the finish mold to the liquid phase of cold shortness is 5-30 cm, then cooling and shaping in water at 5-20 degrees C, and rolling at a speed of 10-20 cm;    (C) water washing for removing the water-soluble solvent and additive at 40-60 degrees C for 0.5-1 hour; washing for 1-2 hours in ethanol or isopropanol to remove the water-soluble solvent or diluting agent at indoor temperature; water washing all the remained solvent at indoor temperature for 1-3 hours; and    (D) airing.