To study the effect of HNS-Ⅳ charge parameters on the performance of exploding foil initiator (EFI),the function time of EFI with different charge parameters was measured. Results show that EFI with charge density of 90% theoretical maximum density (TMD) has the shortest function time and maximum initiation sensitivity. The initiation sensitivity of EFI with charge densities of 60% and 98%TMD is very low. When the charge density is 90%TMD,charge diameter has little effect on the initiation sensitivity and function time of EFI.