Research conclusions: In this paper, the analysis has been made on electric wave transmission performance in free space and the multipath effect is produced by reflection wave and refraction wave. The field strength distributing curve is drawn by theoretical calculation，and the blind spots of signal are analyzed, so the viewpoint of that multi-antennae signal covering with 99% of area is put forward. If the signals of multiple networks are distributed in the metro, it is impossible to separately establish the network for each system, accordingly the concept that the multiple networks signals are combined into one network is used for the design of antenna subsystem for attaining the best result.