To address the problems of single-channel vulnerability， low transmission efficiency， and security risks when combined with the InterPlanetary File System （IPFS） in the existing blockchain covert communication models， a multi-channel covert communication model based on blockchain and social network was proposed. First， the Content IDentifier （CID） returned after uploading secret files to IPFS was split into multiple shares using the Shamir secret sharing algorithm. Second， an embedding algorithm based on Ethereum smart contracts and another based on zero-width characters in social networks were designed to achieve cross-channel collaborative transmission of shares. Third， a redundant share mechanism was introduced， so that the CID could still be reconstructed under unstable network or partial share loss conditions， and the share parameters were supported to be adjusted dynamically to meet different security， latency， and cost requirements. Finally， the receiver was required to extract a sufficient number of shares reaching the recovery threshold from Ethereum and social networks to reconstruct the CID， thereby retrieving the secret information from IPFS. Experimental results show that with baseline parameters， the proposed model requires 21.02 s and only 1.01 USD to transmit 100 MB of data. Compared with comparison models， the transmission efficiency of the proposed model is reduced from the minute level to the second level with the cost reduced by at least 40%， and the model demonstrates superior security and robustness， making it suitable for efficient， secure， and low-cost covert transmission of large-scale data.