Abstract: Pyrite is one of the primary gold-bearing minerals in most gold deposits. In view of the chemistry of crystalline structure, the features of pyrite crystal are analyzed. The mechanism of gold ions (Au⁺ and Au^-)taking the position of ironic and sulphuric ions (Fe²⁺ and S^2-) respectively, and the deposition of gold with macro-form are discussed. Through the study, the authors conclude that the deposition of gold in pyrite crystal is primarily related to the crystal structure of pyrite, especially to the electronic structure of Fe-S, S-S. Au-S and Fe-Au bonds in the pyrite crystal.