In order to study grinding behavior and grinding error,an error analysis model based on vertical grinding process system was proposed.The model was composed of turntable,workpiece,grinding wheel,spindle and other components.The effects of speed ratio,initial roundness error phase,grinding time and spindle rotation error on grinding accuracy were analyzed.The results show that by using the system,the grinding behavior and grinding error can be predicted; when the speed ratio is an integer,the grinding accuracy increases with the increase of the speed ratio; when the speed ratio is not an integer,the change is more complex; the phase of the initial roundness error of the workpiece can not affect the final machining roundness; with the progress of grinding,the roundness error of the workpiece starts to decrease quickly,and then the decreasing trend gradually slows down; among the component frequencies of spindle errors,the third order error causes the largest roundness error and the second order error causes the smallest roundness error.