This paper proposes a security opportunistic routing decision method based on trust mechanism (TOR). In this scheme, every node locally maintains a trust vector to record trust degree of other nodes, which indicates their ability of carry and forward messages. Using layered coin model and digital signature mechanism, the forwarding evidences of relay node signature are bound dynamically on message packet during the relay process, and the message carries evidence chain to the destination node. The node broadcasts periodically the trust vector with signature and time-stamp to network by flooding. Through multi-iteration, the read-only trust routing table (TRT) with multidimensional row vectors is built on every node, which will become the key-player of selecting the next-hop relay node and dividing copy number. The node with greater trust degree is taken as the next-hop relay node. Therefore, the message can be delivered to the destination along the direction of trust gradient increment. Simulation results show that compared with existing algorithms, TOR algorithm can resist the network destruction behavior of malicious nodes and selfish nodes with higher probability of delivery and lower average delivery delay, and it only needs very small buffer and computing ability of node.