Exemplified by a case history, the Houshihua gold deposit in the central-west Inner Mongolia Autonomous Region, the present paper briefly describes the the characteristics of the ductile zones, and advances the new viewpoint of a "diagenetic and ore-forming hydrothermal system of the ductile shear zones". The stuides show that diagenetic processes of ductile shearing consist of the fine granulation process, thermal fluid process, and acidic and alkali metasomatism. In the process of forming such intensive fractures as the ductile shear zones, the side of the thrusting wall was developed in the direction from the relatively deeper part to the crust to the shallower one. The pressure - dropping effect and the dilatational permeation action within the ductile zones themselves contributed to the accumulation of energy gradients (including pressure, temperature and substance) inside the shear zones. As a result, the fluid extensively diffusing in the wall rocks and the lower crust entered into the ductile shear zones. The effect of the "throttle valves" resulted in a metallogenetic hydrothermal fluid system of ductile shearing. The kernel of ore control by the structure of ductile shearing is that the diagenetic mineralization proves to be a unified thermodynamic system, with diagenesis predominant in the early stage and alteration and mineralization predominant in the middle and late stages.