The paper presented illustrates the environmental stability of CoS₂ under varied conditions, and physical or chemical methods for its improvement. The results confirm: the decomposition rate of CoS₂ increases with decreasing temperature, increasing water or oxygen partial pressure. Mixing with molten salt LiCl-KCl was adopted as the physical method to improve the environmental stability of CoS₂, and good result was achieved, which was ascribed to the stronger ability of absorbing H₂O in LiCl-KCl, and blocking the reaction of H₂O and CoS₂. Chemical route was also adopted, by forming a protect layer on CoS₂. The protect layer was formed by using cation exchange method, with FeCl₂ solution under specifically situation, and obvious improvement was observed. Fig. 1 shows the variety of decomposition rate of CoS₂ with temperature in humid (pH₂O~3x10^-2 atm) air.