Cooperative communication has been proven as one of the effective spatial diversity techniques to mitigate channel impairments due to fading. In classical relay selection schemes, plenty of source nodes are supported by a best relay and the transmit power of this relay is equally divided among multiple sources, leading to a low relay power level to help each source devoted and thus an unreliable transmission. To address this issue, we propose a distributed relay selection scheme, where each relay considers the maximum number of source nodes to help without incurring errors. Simulation results show that the proposed scheme has a superior outage performance comparing with other schemes, especially in the networks with 'large number of sources'. Furthermore, the proposed scheme effectively makes use of relay power, and it reduces the total power consumption for relay cooperation.