Phase equilibriums and glassformation in the As2Se3-Bi2Se3-AgBiSe2 system have been investigated using DTA and X-ray methods. Projection of liquidus and solidus surfaces, some isothermal and polithermal sections of phase diagram constructed. It has been established that the system is characterized by formation of wide area of solid solutions on the basis of high temperature cubic modification of AgBiSe2. Glassformation on the basis As2Se3 reaches 15-18 mol%.