Abstract: The ore deposits in Tomorite gold deposit region in Qinghai Province are located in NW-NWW trend fault zones, which are the major ore-controlling structrues in the area. Through thorough analysis of the ore-controlling structures in the area, we found that formation of the fault zones can be divided into three stages, which are ductile shear deformation stage, brittle deformation stage and late reform-destruction stage. The brittle faults superimposed upon the early ductile shear zones are favorable regions for mineralization, and the formation of the ore deposits is related to the ductile-brittle transition of fault zones in the area.Study on ore-controlling structures shows that the ore veins are located near ductile-brittle transition in fault zones. Uplift and denudation after the formation of the ore bodies lead to their exposure near the ground. It is possible that some mylonite-type ore bodies would exit beneath the quartz vein ore bodies, but the tenor of ores would be a little lower. More attentions should be paid to the deep mylonite-type ore bodies in the future work.