Objective：The Tancheng—Lujiang fault (Tanlu fault) belt，as a giant shear zone in eastern China,has been a hot spot among geologists since it was discovered.The Xishanyi pluton，which protolith was monzogranite，located in the west of Feidong group.However，the pluton occurred ductile deformation due to sinistral strike- slip shearing of the Tanlu fault belt.The mylonite with strong deformation is formed on both sides of the pluton，and the gneiss within the pluton is deformed weakly.Due to the serious overburden, only the west side is exposed. In this paper, the structural analysis of mylonite and gneiss are carried out,to investigate the structural deformation characteristics of the Xishanyi pluton. Methods：Detailed field observation，microstructure analysis，estimation of metamorphic—deformation temperature，analysis of tectonic stress field，kinematic vorticity calculation，the fractal dimension of the quartz，and the calculation of differential stress and strain rate of quartz are used to study the Xishanyi pluton． Results: Through the observation and analysis，the dynamic recrystallization type of quartz and feldspar in mylonite is mainly GBM and BLG—SR，respectively.The dynamic recrystallization type of quartz and feldspar in gneiss is SR—GBM and BLG，respectively .In addition，the fractal dimension of the quartz in mylonite is between 1.164~1.173，indicating the metamorphic—deformation temperature of mylonite is between 500～600℃.However it is 400～530℃ in gneiss.Through microscopic analysis and measurement ，the vorticity value Wk is between 0.86~0.94， which is greater than 0.75 and indicates that the shear zone on the west side of the Xishanyi pluton is mainly simple shear，with little component of pure shearing；The results of stress field show that the direction of maximum compressional stress is between 164°~171°.The minimum differential stress is between 20.02～23.08Mpa，and strain rate of the shear zone is between 1.35×10-13～4.93×10-13s-1. Conclusions: Through detailed field observation and indoor analysis on the Xishanyi pluton，we know the pluton participated in the activities of the Tanlu fault belt as a tectonic lenticles.The pluton and the shear zone on both sides constitute the “S—C” fabric.The pluton recorded the activity characteristics of the Tanlu fault belt.