A software system for CNC dressing involute grinding wheel was developed. When the ordinary grinding wheel was used in gear form grinding, the key was to handle the on-line dressing of involute wheel. Based on involute generation principle, an algorithm by taking straight line to approach involute with equal error was mainly studied. The NC program for dressing involute wheel was prepared by using VC++6.0 as programming tool, and wheel dressing experiment was completed. Experimental result shows that the proposed algorithm is valid，and the developed program is feasible with friendly interface. The success of this software system lays the foundation for further developing CNC gear form grinding system.