Phase equilibrium in the systems InAs2S3Se–InAs2SSe3, InAs2SSe3–In3As2S3Se3, InAs2S3Se–In3As2S3Se3, InAs2S2Se2–In3As2S3Se3, (InAs2S3Sе)0.70(In3As2S3Se3)0.30 (е4)–(InAs2SSe3)0.60(In3As2S3Se3)0.40 (e3) were studied using the methods of physico-chemical analysis (DTA, X-ray phase, MSA, measurement of microhardness and determination of density) and state diagram was plotted. It was established that except the latter, all are quasi-binary and belong to eutectic type. The system InAs2S3Se–InAs2SSe3 is characterized by the formation of a new quaternary compound InAs2S2Se2 melting congruently at 615 K. Liquidus surface projection of quasi-ternary system InAs2SSe3–InAs2S3Se–In3As2S3Se3 was constructed. Primary crystallization fields and coordinates of non- and monovariant equilibrium were determined