This paper proposes a channel state information (CSI) weighting combining scheme for a successive interference canceller (SIC). In general, SIC performance is degraded by the estimation errors in CSI caused by interference and temporal channel variations. This paper introduces a scheme to appropriately weight and combine pre-CSI, defined as CSI estimated for transmitting power control (TPC), and post-CSI, defined as CSI estimated in the SIC process. The combined CSI is more robust against interference and temporal channel variation because pre-CSI and post-CSI resist the former and the latter, respectively. Simulation results show that the combined CSI improves the number of simultaneous transmitting terminals (directly related to interference) 17% (vs. post-CSI) and 5% (vs. pre-CSI), and the allowable environmental speed (directly related to temporal channel variation) 50% (vs. pre-CSI).