Objectives:The Yiwulüshan ductile detachment shear zone is located on the northern North China Craton，and strike NE，dips to W—NW，and consists of footwall which composed of ductile shear zone(mylonite zone) and no deformation Mesozoic granite pluton，brittle detachment fault and hangwall sedimentary rocks. In this paper，we focus on the ductile thinning with the Yiwulüshan ductile detachment shear zone. Methods: we use the strain measurement and Polar Mohr diagram to estimate the strain and the kinematic vorticity (Wk) values，and estimate the values of ductile thinning of the Yiwulüshan ductile detachment shear zone. Result: The results of strain measurement using the feldspar porphyroclasts of mylonite within the ductile zone shows the principal axes X＞Y (≈1)＞Z of the strain ellipsoids and that the Xaxis is lengthening，the Yaxes is remaining unchanging and the Zaxes is shortening. The kinematic vorticity (Wk) values，estimated by the Polar Mohr diagram，changed from 0.61 to 0.96 with an average of 0.80，which suggest that the Yiwulüshan ductile detachment zone experienced simpledominated general shearing.  Conclusions: Based on The strain measurements and kinematics vorticity estimation，the ductile thinning of Yiwulüshan ductile detachment shear zone ranged from 10% to 40% alone the sense of detachment. It suggests that it has a positive correlativity between the ductile thinning and strain intensity has，and a negative correlativity with the kinematic vorticity.