A new simple model of grinding force in surface grinding is proposed in this paper. The model is based on the fact that the grinding forces are composed of chip formation force and sliding force. The formula for calculating the tangential and normal grinding force per unit width is obtained based on the classical formulas. The coefficients in the formula are determined experimentally by performing grinding tests at specified conditions. And the influence of processing parameters on friction coefficient is considered in this paper. Effectiveness of this model is proved by comparison of the experimental results and the model calculation results, and the comparison results show reasonable agreement quantitatively.