In the first-level market spectrum market, spectrum allocation is a fundamental access mechanism for licensed spectrum in mobile communication networks. Spectrum Management Organizations (SMOs) authorize and allocate spectrum resources to telecom operators, industrial users and commercial entities. However, existing allocation methods rely on cumbersome approval procedures, leading to inefficiency, prolonged processing times and disclosure of sensitive information. Furthermore, most present centralized methods lack efficient mechanisms to ensure openness and transparency in both spectrum allocation and revocation processes. To address these challenges in the context of 6G networks, a blockchain-based spectrum allocation method is proposed. The proposed solution can not only enable secure and privacy-preserving spectrum resource allocation but also realize certificate transparency and revocation transparency. Theoretical security analysis and proof demonstrate the robustness of the method against security threats inherent in spectrum allocation processes and certificate management.