Abstract: Exact solutions of KdV and mKdV equations can be obtained according to (g/g2) expansion method. Three different solutions can be deduced: hyperbolic function solutions, trigonometric function solutions, and rational functional solutions. Solitary wave solutions can be calculated when special values of the hyperbolic function solutions are properly chosen. Having concluded from the solving of both equations, the (g/g2) expansion method is a well choice of solving nolinear equations which is more convenient, and easy-calculating than (g/g) expansion method and other methods mentioned before.