Abstract: Nenjiang-Heihe tectonic belt is an important mylonite-related gold metallogenic belt in Northeast China, but its tectonic setting and dynamic mechanism remain to be clarified. Yongxin gold mine is a large-scale gold deposit in the southwest margin of the belt, and the characteristics and ductile deformation mechanism of mylonite in this gold mine play an important role in revealing the metallogenic regularity of regional gold mines. Based on the microscopic observations and geochemical analyses of the mylonite characteristics, combined with fractal methods to estimate the deformation parameters(deformation temperature, paleodifferential stress and strain rate), this study elucidated the coupling relationship between ductile deformation parameters and gold mineralization.The results showed the mylonites in Yongxin gold deposit could be divided into protomylonite, mylonite, and ultramylonite, developing augen structures, S-C fabrics, and core-and-mantle structures. The Au content increased significantly at the orebody contact zone and was not affected by mylonitization. The fractal dimension of the mylonite was 0.98~1.09, corresponding to the high amphibolite-granulite facies, with a deformation temperature of 700~750 ℃.The paleodifferential stress was 10.66~38.45 MPa, and the strain rate ranged from 10^-15.50~10^-14.94 s^-1, belonging to low strain rate. This study clarifies that the ductile shear zone of Yongxin gold deposit is formed in a stable tectonic extensional environment characterized by high temperature, low stress, and low strain rate, thereby providing dynamic parameters and theoretical basis for understanding the metallogenic tectonic enviornment of the mylonite-related gold deposits in Nenjiang-Heihe Tectonic Belt.