A microporous polyolefin multilayer film which is used as a separator for a battery is a 3 layer microporous film which is prepared by a wet process to have both surface layers containing polyethylene of 95 wt % or more having a melting temperature of 125° C. or higher, and an inner layer containing polypropylene of 50 to 90 wt % having a melting temperature of 160° C. or higher and polyethylene of 10 to 50 wt % having a melting temperature of 125° C. or higher. A thickness of the film is 9-50/M, a puncture strength is 0.15N//M or more, a permeability is 1.5×10−5 Darcy or more, a multiplication of the puncture strength and the permeability is 0.4×10−5 Darcy·N/μm or more, a shrinkage in a transverse direction at 120° C. for 1 hour is 15% or less, and a melt fracture temperature of 160° C. or higher.