Most cloud providers use centralized servers to manage data. However, centralized servers still suffer the risks of single point of failure and data theft. We add a blockchain to the cloud service and propose a new architecture to manage data. Using blockchain as a connector to utilize the tamperproof, traceable, and data-sharing features of the blockchain to ensure that the transaction data are properly stored in each node. We use the stock simulation trading service to extend and divide the research design into two levels, namely, system and application services. First, we directly write the data into the blockchain. Second, we alternatively store the data in the cloud and then write it into the blockchain. Finally, the two versions are compared and analyzed to investigate their feasibility and performance. At the application service, we implement the smart contract for the existing stock transaction process to achieve real-time settlement.