Through analyzing the principle of spline curve interpolation in CNC machining, a real-time non-uniform rational B-spline （NURBS） interpolation algorithm based on Newton iteration method was proposed. The proposed algorithm firstly controls the velocity design to meet the machining accuracy, then uses the Newton iteration method to calculate the interpolation parameters. The method can avoid derivative calculation of traditional methods. The second order Taylor expansion was simplified into sim- ple linear recursive equation, which can be used to get the initial value of interpolation parameters. Simu- lation and experimental results show that the proposed algorithm has advanced features of good stability and high precision. And the proposed algorithm can meet with the real-time interpolation requirements and reduce the feedrate fluctuation to idea level.