This paper proposes an inter-symbol interference (ISI) suppression scheme using the sub-carrier group selection for orthogonal frequency division multiplexing (OFDM) time division duplex (TDD) transmit diversity. Although transmit diversity is quite effective in improving the transmission performance, the ISI due to the long multipath delays causes the error floor and leads to a loss of the space diversity benefit. To cope with this degradation, the periodic time domain waveform obtained by the even-numbered sub-carrier group is used for the extension of the guard interval. Moreover, the odd-numbered sub-carrier group is also applied to exploit the frequency diversity benefit, which is realized by carrying out the simple frequency conversion at the receiver. To keep the constant transmission rate even in the sub-carrier group transmission, the high-level modulation scheme with power enhancement is applied. The computer simulation results show that the proposed scheme not only prevents the error floor due to the ISI but also achieves the space and frequency diversity benefit without the extension of the guard interval.