The numerical simulation and experiment had been applied to study the cooling of electric cutting tool. Temperature and wind velocity vector of three-dimensional cooling duct were obtained by Fluent. From the numerical simulation, the stagnation flow, reflow and backset which resulted in the poor cooling condition of the electric cutting tool were discussed. By modifying ribs, partition and outlet, a new cooling duct was reconstructed. The cooling effect of the new cooling duct was better than the original one by the experiment test.