Helical gear hobbing processing needs to rely on two sets of electronic gear boxes to control multi axis synchronization.The synchronization error comes from the linear superposition of the rotational motion of hob B axis and the linkage error of workpiece C axis,as well as the axial motion of hob along Z axis and the linkage error of workpiece C axis.Therefore,it is difficult to compensate the helical gear processing error.The C-axis synchronization error signal was collected,the wavelet packet algorithm was used to decompose it.The amplitude distribution law of sub-band signals in different frequency band scale was studied,the error characteristic was identified,and the synchronization error of helical gear processing was reconstructed.According to the error superposition principle,the reconstructed synchronization error was decoupled to each servo shaft participating in the linkage,the NC code was modified,and the error was compensated to the servo shaft in reverse.Finally,through the example of helical gear processing error compensation of Qinchuan YK3126 CNC hobbing machine,the effectiveness of the compensation method was verified,the machining accuracy of helical gear was improved.