MIMO/OFDM is one of the promising technologies to improve the spectral efficiency, enhance system capacity and mitigate intersymbol interference in the fourth generation broadband mobile communication system. In this paper, we aim at the study of a communication system that employs both MIMO-OFDM and adaptive modulation/coding technologies. In this article, the performance of different modulation schemes including fixed modulation/coding and adaptive modulation/coding is analyzed and compared by simulation. We also propose an adaptive modulation/coding algorithm for multiuser MIMO-OFDM system. This adaptive allocation algorithm assigns the subcarriers and bits for users in the system with the minimum total transmission power and targeted bit error rate (BER) based on the time-variant MIMO channel condition. Computer simulation results demonstrate that the proposed algorithm is not only simple but can also have a relative low transmission power compared with the fix BPSK, QPSK and 16QAM modulation schemes.