As has a small diffusion coefficient in HgCdTe material and can form a relatively stable structure, which is widely used in p-type doping of HgCdTe. As doping is an important method in the preparation of p-on-n type HgCdTe infrared detector. In view of the problem that the As activation rate cannot be accurately measured, a low temperature weak p-type annealing assisted hall test method is proposed to obtain the carrier concentration distribution. By comparing with the SIMS test results, the As activation rates in the long and medium wave liquid phase epitaxy HgCdTe material were obtained, and the influence of annealing and other processes on the activation rate after As doping was analyzed.