Trust is a critical factor in enhancing the collaborative efficiency of cross-boundary innovation alliances and driving the process of cross-boundary innovation. Under the background of the integration of the digital and the real economy，the application of blockchain technology has triggered profound and intricate transformations in the multi-source evidence underpinning trust relationships within cross-boundary innovation alliances. This study，grounded in the integration of trust source theory and innovation network theory while incorporating the influence of blockchain technology，constructed an assessment model for trust relationships in cross-boundary innovation alliances based on evidence theory. An empirical analysis was conducted using the C-ITS cross-boundary innovation alliance as a case study. The research findings were as follows:（1） The hybrid evidence fusion rule significantly enhances the reliability of trust fusion results in cross-boundary innovation alliances and effectively mitigate uncertainty. （2） The impact of cross-boundary institutional trust，co-boundary feature trust，and cross-boundary process trust on the overall trust level in cross-boundary innovation alliances diminishes sequentially，with the former demonstrating a synergistic effect when combined with the latter two factors. （3） Under varying levels of trust，the focus on enhancing trust capital shifts accordingly. When trust capital is limited，emphasis should be placed on the interaction between cross-boundary institutional trust and co-boundary feature trust. Once the trust capital stock surpasses the alliance's benchmark threshold，greater attention should be directed toward the coupling enhancement effect between cross-boundary institutional trust and cross-boundary process trust. This research offers valuable insights for cross-boundary innovation alliances to leverage blockchain technology fully for expanding trust capital and holds significant theoretical and practical implications for accelerating cross-boundary innovation and fostering new qualitative productive forces.