In order to study the effect of non-uniform preload on the rotary performance of the bearing-spindle system,the bearing-spindle test bench was tested by applying a controlled preload force,and the least-squares circle method was used to evaluate the shaft trajectory;the effect of non-uniform preload on the radius of the shaft trajectory was investigated at different speeds and operating conditions.The results show that even under no-load,the non-uniform preload of the outer ring of the bearing has different effects on the shaft center trajectory;under radial load,a suitable non-uniform preload can gradually improve the rotational performance of the spindle.