<FONT face=Verdana>The relay selection plays a very important role in cooperative communication systems. In many practical scenarios not all nodes between the source and the destination which can decode information from the source take part in relay

here we propose a cooperative diversity method which randomly selects a node from a set of available relays to forward information towards the destination and then analyze the outage probability of this method. Theoretical analysis and simulation results demonstrate that the upper bound of this outage probability almost does not vary to the number of potential relay nodes

but the bottom bound of this outage probability becomes much smaller as the number of potential relay nodes increases.