The invention discloses a chance relay-selection method for a cooperative communication network under tapping environment. The chance relay-selection method comprises: establishing a wireless cooperative communication network which includes a source node S, a target node D, M standby relay nodes R1, R2, ..., RM, and a tapping user E; transmitting information by a decode forwarding protocol during a transmitting process, wherein the whole transmitting process includes two phases: in the first phase, the source node S broadcasts information to the standby relay nodes, and in the second phase, the optimal relay selection and power distribution are performed, and the selected optimal relay node forwards information to the target node D. The chance relay-selection method for a cooperative communication network under the tapping environment is simple in relay selection and power distribution methods and easy to implement, comprehensively considers channel status information of legal users and the tapping user, can obtain better safe outage probability performance, and is relatively high in practical value.