The work is devoted to the study of a possible technology for the immobilization of mercury in waste, based on the principles of converting mercury and its compounds in waste into mercury sulfide. The purpose of this work is to develop an optimal method for immobilizing mercury in mercury-containing waste, and then compare the effectiveness of various stabilization methods. It is shown in the article that the frequently used immobilization of waste with sulfur may be ineffective and may lead, among other things, to the formation of ionic mercury. Therefore, the paper proposed to use pyrite instead of sulfur to immobilize mercury in waste. It is also shown that this process is more efficient and faster. Even better results are obtained using a mixture of pyrite and elemental sulfur. The analytical method of the mobile mercury and ionic mercury content in the final product estimation was developed. This analytical method is also used for determining mercury in solid samples. This final product is a powder mixture of glass, sulfur or pyrite, mercury sulfide, bentonite, and other mercury compounds including metallic mercury.