Using 5-axis CNC machine tools for high speed machining, once a mutation occurs somewhere in the processing interference and mutations of surface corner, the mutation of tool axis vector may occur rapidly, while the use of traditional methods including retracting and then engaging again, will inevitably lead to reduce the product quality and process efficiency. To solve the above problems, a novelty path generation algorithm for 5-axis high speed machining is proposed. The processes are carried out which are using partial differential equations of heat conduction model and defining the projection parameters of projection region for the calculation of contours within the projection region, selecting out of the temperature contours which meet the processing conditions, defining the mapping rules and planning processing trajectory within the standard parameter domain, then mapping trajectory to the corresponding parameter domain to generate spiral trajectory, and mapping the spiral trajectory to the parametric surface to generate the spiral processing trajectory. This processing trajectory can be achieved without retracting processing. Using the above algorithm to obtain the simulation results, it shows that the new method is superior to traditional processing methods. The results also show that this method can achieve high-speed processing based on the complexity of parametric surfaces and cavity of trimmed surface.