The generation of iron ions in sulfide mineral and their function in oxidation and spontaneous combustion of sulfide mineral are described. The indoor test result of ore samples has shown that the higher the content of iron ions, the faster the speed of sulfide mineral oxidates and the greater the possibility of fire hazard exists. Therefore, the removal of iron ions is the best way to constrain the oxidaton of pyrite and to eliminate the hidden danger of intrinsic combustion. An introduction, to the method of iron ions removal is given.