In order to generate pattern index on video stream in real time and quickly, an index authentication scheme based on Blockchain is proposed for event oriented real-time monitoring video query. By encrypting the secure channel between edge node and fog node, index data can be protected to improve the security of intelligent monitoring system. Firstly, by performing detection and tracking tasks on embedded edge devices, event oriented monitoring service extracts feature information by processing input frames. Then, real-time index service generates a unique index for each frame to prevent malicious modification of the image. Finally, the frame index is input into the Blockchain network and verified through the authentication mechanism based on decentralized smart contract Card. The experimental results show the feasibility and effectiveness of this scheme. The total cost is very low, which is suitable for the application of real-time monitoring video query.