The multi-user multiple-input single-output (MU-MISO) visible light communications (VLC) system have been widely studied in recent years. Operating VLC under different illumination levels is desirable and therefore the need for dimming control mechanism. In this paper, we proposed a novel minimum-mean-squared error based spatial dimming (SD-MMSE) scheme for MU- MISO VLC systems. By taking full advantage of the channel state information (CSI) between the transmitter and the users, we adopted transmit antenna selection (TAS) technique and effectively combined it with MMSE precoding. Dimming control is thus achieved by selecting the optimum light emitting diodes (LEDs) subset. Simulation results show that the proposed SD- MMSE scheme could achieve improved bit-error-rate (BER) performance compared with traditional dimming schemes. These advantages make the proposed scheme a promising candidate that could be applied in MU-MISO VLC systems.