Mechanical analysis for jointed rock mass is very significant in geotechnical engineering. In particular, the mechanical characteristics of jointed rock mass can result in nonlinear response of geotechnical engineering and in consequence mechanical analysis for the engineering is difficult. In order to simulate jointed rock mass, a new equivalent model is proposed for two-dimensional jointed rock mass based on strain energy equivalence principle. Firstly, the equivalent elastic modulus and Poisson's ratio for a horizontal joint in unit square is deduced. Then, the equivalent flexibility matrix for a joint of specified angle in unit square is given. Moreover, the equivalent flexibility matrix for multiple joints, which have different angles in unit square, is obtained. Finally, a numerical simulation is given to verify the model. Compared with other conventional algorithm, the proposed approach has some strong points: it is easy to implement in the finite element program. Furthermore, it provides a new model to compute the deformation of joints and rock and the precision is high.