In wireless communication systems, the use of multiple antennas at both transmitter and receiver, called multiple-input multiple-output (MIMO) architecture, is one of the most promising techniques to improve spectral efficiency and performance communication links. This paper proposed a new scheme of training sequence transmission for estimating the time-varying channel in the MIMO MC-CDMA system. Such training sequences can be regarded as an optimal manipulation by mean of orthogonal design. The proposed scheme can support more number of users than the conventional scheme. The optimum training sequences reduce the complexity of the channel estimation at the compensation of a negligible performance degradation. The proposed estimator was evaluated by computer simulations to demonstrate the merits of proposed technique.