<p>Under the global trend of trade digitalization, the execution of cross-border contracts increasingly depends on the collaborative invocation of multi-chain service systems. However, existing cross-chain solutions still exhibit critical gaps in identity authentication and trusted execution. To address the problems of unverifiable cross-chain identities, ambiguous responsibility of invocation results, and the difficulty of coordinated endorsement across multiple chains, this paper proposes RTIC, a relay-chain-based trusted invocation framework for cross-border trade contracts. The framework adopts the relay chain as a unified coordination hub and constructs a layered architecture to achieve structured encapsulation and unified verification of cross-chain service requests, execution results, and endorsement information. To ensure trustworthy access-chain integration, a Silent-Setup-based Threshold BLS chain-level identity authentication mechanism is designed, enabling aggregatable chain-level endorsement statements. At the consensus layer, a PoVC dynamic committee mechanism is proposed, which combines verifiable random election with a lightweight Byzantine fault-tolerant process to achieve unified confirmation and on-chain recording of cross-chain invocation results. Experimental results demonstrate that RTIC maintains low identity authentication overhead while achieving favorable throughput performance.</p>