The result of TEM analysis of mylonites of the Guandian-Longwangjian fault has verified the existence of this fault and revealed its deep-fault features. The differential stress, strain rate and direction of the movement of the fault during the formation of the mylonites are close to those of the Tan-Lu fault system. The formation of the fault is closely related to the sinistral-slip of the Tan-Lu fault. The deep-fault characters of this fault make it an important regional ore-control structure for gold deposits in the area. The occurrence of the Yanshanian granites indicates that the main sinistral strike-slip movement of the Tan-Lu fault system probably took place during the late Indosinian epoch.