In this paper author has elaborated computer-based model of substitutional solid solution hydrochemical precipitation Ag x Pb 1-x S from the direction of PbS by lead sulfides and silver co-precipitation. According to simulation results concentration areas of forming supersaturated solid solution components with a maximum of Ag 2S up to 12,8 mol.% have established. The adequacy of the proposed computer model has generally confirmed by the results of experimental studies on hydrochemical synthesis of films Ag x Pb 1−x S 1− δ.