In this paper, 2-D numerical simulation was used to simulate the structure of MWIR HgCdTe APD, and the structural parameters of APD devices at 80K were obtained by comparing with the experimental results. At the same time, the influence of dark current mechanism on APD devices at different operating temperatures was studied. The performance of APD devices with the change of each parameter under the condition of high operating temperature was studied. We proposed the optimal HgCdTe APD structure for achieving high performance at 150K. The structure provides an important reference for the subsequent development of APD devices with high operating temperature.