By single factor experimental method, taking critical process parameters of cylinder stagger spinning including reduction ratio, feed ratio and radial offset as variable, and the roundness error of external surface of the workpiece after spinning judged by the least square principle method as the evaluating index, the influences of the above parameters on the roundness error were obtained. The result shows that when the reduction ratio is from 25% to 35%, it has little effect on the roundness error. However, when the reduction ratio surpasses 35%, the roundness error increases with the increase of reduction ratio, and the roundness error first increases and then decreases with the increase of feed ratio. A relatively small radial offset, which means the increasing of wall thickness thinning amount for the first roller is beneficial to reduce the roundness error.