Abstract: For multiple-relay cooperative networks with multiple antennas deployed at source and destination nodes, we investigate the outage performance of selection based semi-blind amplify-and-forward (AF) relaying, where transmit beamforming (TB) is conducted at source transmission and maximum ratio combining (MRC) at destination reception. Based on the Kolmogorov-Smirnov test, we analyze the impact of the configuration of destination antennas on the outage performance under arbitrary Nakagami-m fading channels. Results reveal that increasing the number of destination antennas is not necessary for an improvement of outage performance with any Nakagami-m parameter. Inspired by this fact, an approximation is proposed for the optimal selection. Simulation results show that the approximation is an efficient selection method.