A two-branch transmit method based on the weighted-type fractional Fourier transform (WFRFT) is proposed to improve the bit error rate (BER) performance of multi-input multi-output (MIMO) systems. The signal to be transmitted is first sent into the information modulation and synthesis module of the transmitter. Then the proposed method is accomplished in a two-step manner. Specifically, the transmitter first decomposes the transmission signal into four way signals. Then, the four-way transmitting signals are combined into two-way signals by time-frequency combination and are transmitted via two independent antennas. The signal is received by single antenna at the receiver. And inverse-WFRFT is performed such that the transmission signal can be recovered reliably. Numerical results show that the proposed scheme leads to a significant performance advantage, in terms of both BER performance and robustness against doubly-dispersive fading, compared with the Alamouti space-time block coding.