Abstract: This paper considers MIMO cellular downlink model with 3 cells and 2 edge users in each cell. By mean of orthogonal-triangular decomposes of the joint channel matrix, the equivalent system model is derived, which has the same degrees of freedom with the original model. Based on the new model, the paper proposes a linear interference alignment algorithm to align and eliminate inter-cell and intra-cell interference according to different interferences from different cells. Before the signals have not received by the users, the proposed algorithm takes advantages of the channel decomposition to eliminate half of inter-cell interference, so as to reduce the number of the receiving matrix and simplify the complexity in receivers. The simulation results show that for given the antenna configuration, system capacity and energy efficiency have significantly improved with the increase in the data stream. In the case of the same degree of freedom, the number of antennas has a greater impact on system capacity and energy efficiency.