present, edge cloud is becoming more and more important as it provides computing resources required by mobile terminals. The online edge cloud resource trading mechanism has become one of the most important ways for edge cloud resource sharing, attracting much attention. In this paper, we have proposed a Blockchain-based Privacy-preserving Combinatorial Double Auction (BPCDA) mechanism, which combines trustworthiness, truthfulness and privacy protection for the first time. Firstly, BPCDA avoids dependence on third-party brokers by adopting blockchain. Secondly, we draw on the economic theories, and then adopt double auction to ensure the truthfulness of bids while participants in the auction are composed of multiple sellers and multiple buyers. Lastly, we make fell use of the differential privacy mechanism on the blockchain to avoid privacy leakage. Through simulated experiments, we verify the superior performance and practicality of our proposed edge cloud resource trading mechanism.