Abstract: Average symbol error rate(ASER)of multiple-input multiple-output(MIMO)systems employing two transmit antenna selection and orthogonal space time codes over arbitrary Nakagami fading channels is investigated in this paper.Using the moment generating function based method,we derived the exact ASER closed-form expressions of binary phase shift keying/frequency shift keying(BPSK/BFSK),multiple phase shift keying(MPSK) and multiple quadrature amplitude modulation(MQAM) with coherent detection.Then the system performance under different conditions was evaluated through numerical simulations.The accuracy of the analytical results was verified.