In this paper， an instantaneous milling force prediction method based on the optimal variable weight method of spindle and feed axis currents is proposed. Firstly， the mapping relationship between the spindle current and the x-direction instantaneous milling force is analyzed， and the delay effect of the current signal is considered based on the cross-correlation method， then based on the Devavit Hartenberg （DH） method， the kinematic modeling of the five-axis machine tool is carried out， and the driving torque of the feed axis is mapped from the machine tool coordinate system to the tool coordinate system， and the relationship between the driving torque of the feed axis and the instantaneous milling force is obtained based on the force Jacobian matrix. Finally， based on the optimal variable weight method， the influence of the spindle and feed shaft currents on the instantaneous milling force is comprehensively considered， and the instantaneous milling force prediction experiment is carried out on a five-axis machining center. The prediction error of the instantaneous milling force of the optimal weight method is within 10%， which can effectively predict the instantaneous milling force of the machining process.