This paper analyzes the tool path generation of the microlens arrays by the single point diamond (FTS) turning,while focuses on the algorithm of tool radius compensation. Firstly, the mechanism of the fast tool servo machining process is introduced. Secondly, the tool path generation for FTS is calculated. The algorithm of tool radius compensation and the form error of the microlens is analyzed. Subsequently, the transitional zone is research, base on the algorithm of tool radius compensation, the optimized algorithm is proposed. Finally, using the optimized algorithm generate the tool path. Modeling of the tool path with the optimized algorithm of tool radius compensation is simulated with MATLAB. The simulation of the 3-D microlens arrays with the algorithm of tool radius compensation has done. According to the modeling of the simulation, algorithm of the radius compensation is discussed. The results show the optimized algorithm can improve the form accuracy of the microlens. The optimized algorithm is practical significant in the tool path generation.