Abstract: In the practical communication systems, the relay can't be completely trusted, so the research on untrusted relay is very necessary. Based on the three-node untrusted relay networks without the direct link, this papper aimed to introduce the power allocation factor in the cooperative interference model, and calculate and analyze the outage probability and ergodic secrecy capacity of the system on two kinds of amplifying coefficients. We first derived the secrecy outage probability on the average amplifying coefficient. Subsequently, on the basis of the same power allocation factor, the adaptive instantaneous amplifying coefficient was used and the lower bound of the secrecy outage probability was derived. For comparison purposes, we gave the ergodic secrecy capacity of the system. Finally, the simulation results confirmed that the derived outage probability and ergodic secrecy capacity was exact, numerical simulations show that the introduction of power allocation factor can reduce the outage probability and improve the ergodic secrecy capacity of the system, the performance of the system on the instantaneous amplifying coefficient is better than the average amplifying coefficient.