In this paper, we propose a simple rate-one space-time-frequency block code (STFBC) for multiple input multiple output (MIMO)-orthogonal frequency division multiplexing (OFDM) system based on linear constellation precoding (LCP) and coordinate interleaving (CI). It is an attractive solution to get a high data rate transmission scheme in a multi-path fading environment. Firstly applying LCP for every input symbol sequence, the proposed scheme can get the frequency diversity gain, secondly applying CI to the LCP transformed symbols, the proposed scheme can reach transmission rate one and can improve the bit error performance of the system, at last, the new symbol sequences after two transformations are sent to the STFBC encoder, and the encoded symbols are sent out from different antennas. Simulations show that compared with the traditional space-time-OFDM (ST-OFDM) system, our scheme can get more diversity gain, higher frequency efficiency and better bit error performance but acceptable computing complexity.