Abstract: Engine crankshaft production line requires high reliability and accuracy stability for the oscillating grinding machine. Based on the field contour error data of the crankshaft, the mapping relation between the contour error of the crankshaft and the axis position control error of the oscillating grinding machine can be obtained. There will be great significance for the axis performance predication and the reliability maintenance of the oscillating grinding machine. Firstly, a calculation method from the axis position control error of the oscillating grinder to the contour error of the crankshaft is presented. Secondly, the contour error analysis method based on variational mode decomposition (VMD) is proposed. Lastly, through the grinding experiments, the error data is acquired and measured to calculate and analyze the error data by using VMD method for obtaining the mapping relationship between the crankshaft contour error and the axis position control error. The conclusion shows the two IMF (intrinsic mode functions, IMF) components of the crankshaft contour error that are analyzed by VMD correspond to the contour error caused by X-axis and C-axis position control error respectively. Therefore, the proposed method can realize the axis performance prediction of the oscillating grinder.