<p>In a typical distributed network such as blockchain, blockchain oracles play the role of a bridge between off-chain data and on-chain smart contracts. However, blockchain oracles themselves cannot guarantee the security of data outside the blockchain. Since external data sources outside the blockchain are usually not controlled by the blockchain network, malicious attackers may tamper with data or forge information, thereby affecting the execution of smart contracts and causing inaccurate or erroneous contract results. To address this issue, we propose a blockchain oracle multi-layer retrieval integrity verification mechanism, which combines the Shamir threshold signature scheme for double verification to ensure the integrity of external data source data. At the same time, the mechanism combines the Merkle hash tree with the signature chain structure to construct a multi-layer cascade verification framework, which further ensures the security of external data sources. In addition, we also proposed a data source reputation management system, which uses a scoring mechanism to evaluate the accuracy and immediate responsiveness of historical data to enhance the reliability of data sources within the oracle framework. Both theoretical analysis and experimental results show that the proposed method effectively solves the problem of insufficient data source reliability.</p>