When measuring the transient response of medium-wave HgCdTe photovoltaic devices,? the surface position of the device irradiated by the laser spot is far away from the photosensitive surface, the device presents a special bimodal pulse response phenomenon. It is analyzed that the abnormal double pulse phenomenon is due to the time difference between the drift of minority particles in the photosensitive region and the diffusion of minority particles collected laterally outside the photosensitive region. By applying reverse bias to the device, the impulse response changes from bimodal to unimodal with the increase of reverse bias, which verifies that the minority lateral collection is the main reason for the bimodal formation of the device. The minority carrier lifetime of P-region materials is obtained by fitting the second peak. Comparing the minority carrier lifetime obtained from the transient response with the theoretical calculation of the P-type HgCdTe material and the photoconductivity decay method, it is found that the trend of the minority carrier lifetime obtained from the three methods with temperature is basically the same, which indicates that the minority carrier lifetime of HgCdTe material can be obtained from the transient optical response.