SIMS (secondary ion mass spectrum) and variable temperature Hall measurement were employed to study the doping of Ag and the electrical properties of Ag doped HgCdTe films grown by LPE. The results show that the Ag doping in HgCdTe by soaking HgCdTe in AgNO 3 solution is effective and the dopant concentration is equal to the Hg vacancy concentration of undoped HgCdTe film. After Ag doping, the acceptor energy of p type HgCdTe has an obvious decrease. It was also found that the electrical properties of Ag doped HgCdTe films can keep stable at room temperature.