Abstract In this paper, we investigate the physical layer security (PLS) in wireless ad hoc networks (WANETs). For fixed transmission distance model, we introduce the jammer selection scheme to enhance the secrecy transmission capacity. The jammer can prevent the eavesdropper from stealing information by sending the interference signal to the eavesdropper, thereby improving the security of the system. Based on the probability density function (PDF) and cumulative distribution function (CDF) of a random variable, we establish the expression of secrecy outage probability (SOP), a main metric in PLS. Finally, simulated results validate the effectiveness of selecting the appropriate jammer and theoretical analysis.