The FEM has been widely adopted to solve electromagnetic field problems. The accuracy of FEM is highly effected by the number of system units and the complexity of computational order,leading to low computational efficiency. In order to improve the computational efficiency of FEM,gradient smooth is introduced into numerical calculation of electromagnetic field,then a new method of ES-FEM is proposed. The electromagnetic field of infinite straight grounding slot and Electric Vehicle are simulated with MATLAB. The results shows that smooth gradient operation makes the discrete system closer to the continuous system,increasing the accuracy and the efficiency of FEM.