Abstract: Coordinated Multi-point Transmission (CoMP) is one of the key technologies of future wireless communications. Base station (BS) in different cells share in different extent both channel state information and data signals of their respective users to convert conventional interference to useful signals, which increases spectrum efficiency and greatly improves the quality of service of the users in cell edge region. In this paper, Block Diagnalization (BD) algorithm which designs proper precoding vectors in the null space of interfering channels in order to completely mitigate interference is applied in multicell joint transmission and compared with other algorithms, such as zero forcing algorithm, minimum mean square error algorithm, time division multiple access and single-user eigenbeamforming. The principles of interference mitigation and macrodiversity gain of BD are analyzed from the view of spatial dimension and the performance corresponding to each algorithm is discussed. Simulation results show that BD outperforms the algorithms aforementioned. Meanwhile, coordinated BD is compared with uncoordinated BD.