Abstract: For the packet loss behavior of the malicious node collusion in the mobile Ad hoc network environment,this paper presents a detection method against colluding nodes.This detection method focuses on cooperation monitoring of guard nodes and computes the trust values of transmission link with the monitoring results between source node and related guard nodes,and then applies the link trust values to avoid colluding nodes.The NS2 based simulation results show that the proposed method can effectively reduce the probability of misbehaving routes caused by colluding nodes and improve the packet delivery rate.