Abstract: The crystal forms and geochemical characteristics of the pyrites in the Katbasu Au deposit have been studied by using the optical microscope and electron probe micro methods in this paper. According to their occurrences, these pyrites can be divided into three types:idiomorphism-subhedral pyrite, anhedral cataclastic pyrite and stockwork pyrite filled with chalcopyrite. The gold mainly existed within pyrite with two forms:native gold and micro-ultramicroscopic inclusions. The native gold occurred as fissure gold, intercrystalline gold or inclusion gold. The Co/Ni ratios of these pyrites range from 3.04 to 83, showing the origin of hydrothermal solution.The characteristics of trace elements show that the Katbasu gold deposit was formed in a high temperature environment, which was related with magmatic hydrothermal, showing the features of deep-source ore-forming materials.