In order to improve the bit error rate (BER) of multiple-input multiple-output orthogonal frequency diversity multiplexing (MIMO-OFDM) system in Nakagami-m channels, the model used rate-compatible punctured convolution (RCPC) and space-time block code (STBC) at the transmitter, maximum ratio combining (MRC) at the receiver was put forward. The signal-to-noise ratio (SNR) of the MIMO-OFDM system in Nakagami-m channels was studied, the expression of BER was given and the average BER upper limit after RCPC encode was further presented. Simulation result shows that the BER performance and the diversity gain of MIMO-OFDM with RCPC encoding achieve much improvement than the system with no RCPC. Owing to the free distance becomes shorter with the increase of code rate, the BER performance and the diversity gain of RCPC encoded MIMO-OFDM decreases a little