A composite film, a manufacturing method for the same, and a battery comprising the composite film are provided. The composite film includes a first layer and a second layer on a side of the first layer. The first layer includes a first polyolefin. The first polyolefin has an orientation function of at least 0.6. The first polyolefin has a repeating unit of wherein R is an alkyl group having 2, 3, 4, or 5 carbon atoms. The second layer includes a second polyolefin. The second polyolefin has an orientation function of at least 0.5. The second polyolefin has a repeating unit of wherein A is a hydrogen or a methyl group.