The tracking lag error of a single axis in non-circular grinding is hard to be reduced due to the big inertia of grinding carriage and the large acceleration of crankshaft. Thus, it’s unsatisfied to improve the contour precision of crankpin just by enhancing the tracking precision of a single axis. To obtain a more accurate contour, the cross-coupled control system is designed based on the approximation that the coupled motion between the rotation axis of crankshaft and the linear axis of grinding carriage is simplified as the coupled motion between two linear axes. And then the control strategy that the parameters of cross-coupled control system are variable along the motion path of crankpin non-circular grinding is proposed to make up for it deficiency in the control of nonlinear path. To minimizing the contour error, differential evolution algorithm is also introduced to optimize the control parameters segment by segment. The simulation results demonstrate the theory contour precision of crankpin non-circular grinding is advanced obviously by the cross-coupled control with variable parameters in comparison with the common cross-coupled control.