The invention relates to the field of lithium-ion batteries, in particular to a method for preparing a composite lithium-ion battery separator through electrostatic spinning/electrostatic spraying. The method specifically includes the steps of firstly, adding high molecular polymer into an organic solvent, dissolving the high molecular polymer through mechanical stirring to form a transparent solution, and obtaining an electrostatic spinning solution; secondly, mixing inorganic nanometer particles with the high molecular polymer and adding the mixture into the organic solvent, and conducting mechanical stirring to obtain inorganic nanometer particle suspension liquid; thirdly, conducting electrostatic spinning on the spinning solution prepared in the first step to prepare a lower layer nanometer fiber film, and enabling the inorganic nanometer particle suspension liquid prepared in the second step to be deposited on the lower layer nanometer fiber film through electrostatic spraying to obtain an interlayer; finally, receiving an electrostatic spun nanometer fiber layer on an inorganic particle layer to obtain the composite lithium-ion battery separator. The composite lithium-ion battery separator has the high imbibing rate and good electrochemical stability under the room temperature and has good heat shrinkage resistance performance at the same time.