The response law of output signal for irradiated and unirradiated pixel in PV-type HgCdTe linear array infrared detector was researched when energy density of nanosecond pulse laser, less than destroyed threshold, was increased. The features of two-stage response of base signal and six-stage response of optical signal were pointed out, the energy density threshold range of each response phase was also given; some abnormal response phenomena such as zero voltage output of base signal integral jumping, sag output-recovery-convex of optical response signal were discovered. Based on the above results, from the point of view of readout circuit and thermo-induced electrodynamic force, the mechanism of abnormal response was revealed. We hope to strengthen the deep understanding of the photoresponse characteristics of HgCdTe array infrared detector, and provide inspiration for the technical innovation of this kind of device.