Abstract-The existence of selfish nodes and malicious nodes pose a significant threat to the complex environment of opportunistic network. In order to improve the transmission security in bad environment, a multi-dimensional trust model GRATM(Grey Relational Analysis Trust Model) based on gray relational degree and cooperative computation is proposed which may improve the success rate and reduce the delay during the process of transmission. GRATM adopts multi-dimensional parameters, the parameters are fused and updated dynamically, and the total trust value is calculated by direct interaction combine with other nodes recommendation trust value. GRATM is based on gray relational analysis, the weight coefficients of the direct trust value are reasonably distributed, and the recommendation trust value is calculated by the neighbor nodes. Trust information is sent to other nodes and exchanged with each other through regular sending package. Compared with Direct, MaxProp, and Direct Delivery, GRATM has the advantages of balanced transmission success rate, transmission delay and performance.