With the application of network video platforms (NVP), network videos often face copyright infringement and cross-platform copyright detection issues when shared across different video platforms. Therefore, this study proposes a blockchain-based cross-platform network video copyright protection scheme (BCVCP), which aims to protect network video copyrights across platforms by means of blockchain and through ownership sequence (OS) generation and detection. This study includes identity authentication, keyframe extraction, ownership sequence generation and detection, and network video control management. Specifically, before operations such as video uploading or access, identity authentication needs to be carried out to ensure identity information security. Secondly, during the process of uploading network videos, an ownership sequence is generated and stored in distributed nodes. Then, the keyframes of the video are extracted and the generated ownership sequence is embedded into these keyframes. Finally, smart contracts are invoked for cross-platform ownership sequence detection and network video dissemination management to avoid infringement behaviors. In the experiments, the robustness of ownership encoding quality and ownership recognition during cross-platform network video transmission is verified, thereby protecting the copyright of network videos.