We propose a water-filling power allocation scheme for Turbo-BLAST system in the presence of channel state information imperfection. Subjected to the total transmit power constraint, the water-filling rule is used to allocate proper power for every sub-channel in order to improve channel capacity performance based on the imperfect channel state information. Simulation results show that the proposed algorithm is effective for Turbo-BLAST system to improve channel capacity performance especially in the lower signal noise ratio region and/or large antenna systems in the presence of channel state information imperfection.