Provided is a microporous polyolefin composite film with a thermally stable porous layer at high temperature, particularly, to the microporous polyolefin composite film in which the thermally stable porous layer at high temperature, which contains organic or inorganic particles and heat-resistant polymer having aromatic ring in main chain and also having a melting temperature or a glass transition temperature of 170 to 500° C., is formed on one surface or both surfaces of a polyolefin microporous film by a phase separation, wherein the composite film with the porous layer has a permeability of 1.5×105 to 20.O×IO 5 Darcy, a meltdown temperature of 160 to 300° C., a MD/TD shrinkage of 1 to 40% at a temperature of 15O° C. for 60 minutes.