Exploiting and sharing unlicensed spectrum resources among cellular and WiFi networks is critical for the fifth-generation (5G) and beyond networks due to the severe spectrum shortage and huge traffic demands. While distributed consensus with blockchain has been considered to realize fair and efficient spectrum sharing, the existing mechanism is not adaptive to wireless network traffic with diverse QoS requirements in dynamic environments, which can result in significant consensus overhead and low levels of QoS. To tackle the above problems of static consensus adopted by the existing works, we propose a two-layer blockchain framework with intelligent consensus scheme for distributed spectrum sharing. Specifically, we proposed a two-layer blockchain architecture including a global blockchain and a local blockchain, and adopt a lightweight Proof of strategy (PoG) consensus mechanism. The local blockchain is dedicated to making spectrum allocation strategies, while the global blockchain is responsible for the management and coordination of the local blockchain. Deep reinforcement learning model is designed for the global blockchain to learn the relationship between the consensus period of the local blockchain and the utilization of the allocated spectrum and maximize the throughput of local heterogeneous networks. Furthermore, we model and analyze the performance of PoG in complicated interference environments. The Lagrange method and the relaxation method are used to transform an NP-hard problem into a fractional programming problem that can be solved iteratively. Simulation results show that the proposed architecture and intelligent consensus mechanism can significantly improve system throughput and adapt to the dynamic environment with complicated interference.