Trusted connect architecture (TCA) technology was introduced to solve the problem of trusted connect between networks in "Pushing Forward the Internet plus Advanced Manufacturing" plan. Based on the idea of TCA technology, this study proposed a trusted connection protocol (TCA-SNI) for trusted authentication and evaluation between networks. The two-way authentication process is introduced and the interaction of TCA-SNI is given. The extended SVO logic system is used to infer the protocol logicalness, which proves that the protocol is safe and reliable. The protocol is detected using the Dolev-Yao model. Experimental results show that the proposed protocol has achieved the security goal, and can withstand attacks in the real network.