Using DSK and quantitative DTA methods the thermodynamic functions of phase melting and polymorphic transformations of AgBiX2 (X-S, Se, Te) compounds have been determined. The comparative analysis of the obtained results with the literary data and values ΔSm calculated in some approximations has been carried out. The conclusion about significant change in the structure of near order of AgBiSе2 and AgBiTe2 compounds at melting made.