Authors represent a computer model for supersaturated solid substitution solutions hydrochemical synthesis in PbS – CuS system by joint sedimentation of metal sulphides. The ability to form supersaturated solid solutions Cu xPb 1−xS with CuS content up to 2.6 mol.% is also represented. Experimental study results of hydrochemical Cu xPb 1−xS films synthesis have in general confirmed their calculated composition data.