A downlink beam forming method in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system, comprising: acquiring spatial covariance matrixes of all uplink slot interference user signals by the following formula to obtain M spatial covariance matrixes, R I m = E H I m H I m H, m = 1, ⋯, M, where E H I m H I m H represents an operation to solve a mathematical expectation of a random variable, M is the number of the interference user signals, H I m represents multiple antenna channel estimation of the m th interference user, and H I m H represents a conjugate transpose operation of matrix H I m, and determining downlink slots in which the interference user signals locate; obtaining an interference spatial covariance matrix of each downlink slot based on the downlink slots in which the interference user signals locate and the spatial covariance matrixes of the interference user signals by the following formula to calculate the interference spatial covariance matrix of each downlink slot, R I, n = ∑ ∀ u m | t d m = n R I m, where u m represents the m th interference user signal, t d (m) represents the downlink slot in which the m th interference user signal locates, and n represents the number of any downlink slot; determining beam forming weight coefficients of downlink expected user signals based on the interference spatial covariance matrixes of each downlink slot and spatial covariance matrixes of downlink expected user signals by the following formula to calculate the beam forming weight coefficients of the downlink expected user signals, w k = arg max w w H R xx k w w H R I, n + λ I w, where k is a positive integer, w represents any variable, w H represents a conjugate transpose operation of w, I represents a unit array of antenna dimensions, λ represents noise power or a constant factor proportional to the interference power, and w(k) represents the beam forming weight coefficient of the k th downlink expected user signal; and implementing beam forming based on the beam forming weight coefficients of the downlink expected user signals by the following formula to calculate the transmitting sequences, s k a = ∑ k = 1 K s k w k a k, where S k a represents the transmitting sequence of the ka th antenna, s ( k) represents the transmitting sequence of the k th downlink expected user signal, ka represents the ka th antenna, and w k a k represents the beam forming weight coefficient of the k th downlink expected user signal at the ka th antenna. acquiring spatial covariance matrixes of all uplink slot interference user signals by the following formula to obtain M spatial covariance matrixes, R I m = E H I m H I m H, m = 1, ⋯, M, where E H I m H I m H represents an operation to solve a mathematical expectation of a random variable, M is the number of the interference user signals, H I m represents multiple antenna channel estimation of the m th interference user, and H I m H represents a conjugate transpose operation of matrix H I m, and determining downlink slots in which the interference user signals locate; obtaining an interference spatial covariance matrix of each downlink slot based on the downlink slots in which the interference user signals locate and the spatial covariance matrixes of the interference user signals by the following formula to calculate the interference spatial covariance matrix of each downlink slot, R I, n = ∑ ∀ u m | t d m = n R I m, where u m represents the m th interference user signal, t d (m) represents the downlink slot in which the m th interference user signal locates, and n represents the number of any downlink slot; determining beam forming weight coefficients of downlink expected user signals based on the interference spatial covariance matrixes of each downlink slot and spatial covariance matrixes of downlink expected user signals by the following formula to calculate the beam forming weight coefficients of the downlink expected user signals, w k = arg max w w H R xx k w w H R I, n + λ I w, where k is a positive integer, w represents any variable, w H represents a conjugate transpose operation of w, I represents a unit array of antenna dimensions, λ represents noise power or a constant factor proportional to the interference power, and w(k) represents the beam forming weight coefficient of the k th downlink expected user signal; and implementing beam forming based on the beam forming weight coefficients of the downlink expected user signals by the following formula to calculate the transmitting sequences, s k a = ∑ k = 1 K s k w k a k, where S k a represents the transmitting sequence of the ka th antenna, s ( k) represents the transmitting sequence of the k th downlink expected user signal, ka represents the ka th antenna, and w k a k represents the beam forming weight coefficient of the k th downlink expected user signal at the ka th antenna.