The invention relates to a composite coating lithium-ion battery separator. The composite coating lithium-ion battery separator is composed of a base film, an aramid fiber coating coated on one side of the base film and a PVDF coating coated on the other side of the base film; the aramid fiber coating is obtained by an aramid fiber sizing agent after coating, soaking and drying, and the thickness of the coating is 0.5-4 microns; the PVDF coating is obtained by a water-based PVDF sizing agent after coating and drying, and the thickness of the coating is 0.1-2 microns. The invention also provides a preparation method of the separator. According to the composite coating lithium-ion battery separator and the preparation method thereof, the separator has the characteristics that the aramid fiber coating is good in thermal performance and mechanical performance and the PVDF coating has good wettability and liquid retention property for electrolytes, can effectively adhere batteries and pole pieces and is little in environmental pollution, and is beneficial for preparing lithium-ion batteries with longer cycle life and higher safety. Tests indicate that the separator has good air permeability, liquid absorption rate, thermal contraction and tensile strength, so that the cycle life of the batteries can be obviously prolonged by using the lithium-ion batteries prepared by the separator.