The prosperity of the low-altitude ecology has continuously promoted the transformation of intelligent network services from the terrestrial to the low-altitude airspace. Low-altitude services and applications have become large-scale， collaborative， and intelligent. These trends have put forward extreme requirements for cross-domain collaboration capabilities， processing efficiency， and the security and trustworthiness of data and operations. Low-altitude intelligent network cluster collaboration using multi-device joint computing can improve the processing efficiency of complex and large-scale tasks in low-altitude intelligent networks. However， the existing schemes still have problems such as lack of cross-domain collaboration， deficiency in security and trustworthiness， and insufficient flexibility in centralized resource scheduling. Blockchain has the characteristics of immutability， openness， transparency， and collective maintenance， which is suitable for establishing efficient collaborative trust. This paper proposes a blockchain-enhanced trustworthy collaboration architecture for low-altitude intelligent network to provide on-chain cross-domain collaborative computing and trusted status synchronization services among heterogeneous low-altitude intelligent devices. We also design a multi-level consensus protocol to ensure the security and trustworthiness during the collaborative computation process. And we further analyze the freshness of the on-chain status， and propose an on-chain state correction algorithm and an efficient cluster-forming strategy for low-altitude intelligent nodes based on a queueing model. The simulation results show that the proposed architecture and protocol can improve the overall performance in terms of collaborative processing efficiency and network resource utilization.