An novel algorithm was presented in regard to the avoidance of interference in normal tracing grinding. The mathematic model of the algorithm was established based on the geometric characteristic and the kinematic relationship between the wheel and the workpiece. The algorithm was simulated and applied in the NC profile grinding. The simulation and experiment both show that the algorithm is effective in avoiding interference in normal tracking grinding. The interfering points on the workpiece could be examined and the optimum approximated normal tracking angle could be calculated based on  this algorithm.