Three different passivation films were used to prepare InSb detectors for testing the current–voltage(I-V) characteristic curves of chips with different perimeter–area ratios. The influence of surface leakage current on the performance of an InSb detector was analyzed by comparing the dark-current density at a bias voltage of ?0.1 V. The test results indicated that SiO2+SiNx passivation could significantly reduce the surface dark current. The capacitance–voltage(C-V) test results also demonstrated that the composite passivation film could significantly reduce the interface fixed charge. A composite passivation-film process was applied for the preparation of a 128?128 15-?m InSb focal plane detector. The optimal value factor of the detector chip was R0A ≥5?104·cm2, which was much higher than that before the test (R0A≈5×103·cm2).