Phase equilibria in the InSe–CaIn₂Se₄ system were investigated using the methods of physico-chemical, as well by measurement of microhardness and microstructural analyses. It has been established that the cut is a quasibinary section of the ternary systems Ca–In–Se. Diagram of state in the system is of eutectic type. At room temperature the InSe based solubility reaches 2 mol %, CaIn₂Se₄, while based on  to CaIn₂Se₄ – 5.5 mol % InSe