NOVELTY - Microporous polyolefin multilayer film is prepared by melting and mixing mixture having (wt.%) polyethylene (20-50) with a melting temperature of greater than or equal to 125 degrees C and diluent (80-50), and mixture having (wt.%) propylene (20-70) with melting point of greater than or equal to 160 degrees C and heat-resistant filler (80-30) having a melting temperature of greater than or equal to 170 degrees C; forming blended melt from mixtures to multi-layered sheet of 2 or 3 layers; forming film by stretching multi-layered sheet; extracting diluent from film; and heat setting film.    USE - Method for preparing microporous polyolefin multilayer film (claimed) used to manufacture secondary battery.    ADVANTAGE - The film has low shutdown temperature and high melt fracture temperature, high strength and stability, and high permeability; and produces secondary battery having high capacity and high power.    DETAILED DESCRIPTION - Preparation of microporous polyolefin multilayer film comprises melting and mixing mixture having (wt.%) polyethylene (20-50) with a melting temperature of greater than or equal to 125 degrees C and diluent (80-50), and mixture having (wt.%) propylene (20-70) with melting point of greater than or equal to 160 degrees C and heat-resistant filler (80-30) having a melting temperature of greater than or equal to 170 degrees C; forming blended melt from mixtures to multi-layered sheet of 2 or 3 layers; forming film by stretching multi-layered sheet; extracting diluent from film; and heat setting film. The pores of polyethylene layer are micropores fabricated by stretching and extracted after separating phase of polyethylene and diluent and having an average size of greater than or equal to 0.1 mu m; and pores of polypropylene and heat-resistant filler layer are macropores fabricated by cracking interface between polypropylene and heat-resistant filler and having average size of 1-50 mu m, and microporous polyolefin multilayer film having thickness of 9-30 mu m, puncture strength of greater than or equal to 0.15 N/ mu m, permeability of 1.5x 10-5 Darcy or more and melt fracture temperature of greater than or equal to 170 degrees C.