Abstract: Aiming at the multi-user massive multiple-input multiple-output(MIMO) system under TDD mode, beam domain decomposition and SVD are used in the channel estimation of the system at the same time in this paper. When the base station equipped with a large number of antennas, the problems such as channel estimation accuracy, pilot overhead and complexity of channel estimation algorithm will be the key factors that affect the performance of massive MIMO system. By using the beam domain decomposition theory, multi-user massive MIMO system can be decomposed into multiple single-user massive MIMO system, and modeling the channel from the beam domain, which reduces the pilot overhead while also reducing the channel estimation error. In addition, the use of SVD to optimize the channel autocorrelation matrix can further reduce the complexity of the channel estimation algorithm. Based on the above two points, this paper proposes a massive MIMO channel estimation scheme based on beam domain decomposition and SVD, and deduces the closed expression of the estimated error covariance matrix. The simulation results show that compared with the similar scheme, the proposed scheme has better channel estimation performance.