The Internet of Things (IoT) has been applied in many fi eldsof science, technology, economy, and society, including agriculture, aquaculture, the environment, and smart city management. How- ever, storing and sharing data in IoT applications face many chal- lenges in ensuring data integrity and security. Because IoT data collection devices in a centralized model are frequently limited in their security capabilities and are vulnerable to att acks, blockchain technology is rapidly developing many key features to improve data security and sharing. Th is study aims to employ blockchain technology to enhance the security and data integrity of IoT ap- plications. Th e system used a private blockchain network built on the GoQu orum platform. Th e Solidity programming language was used to develop the smart contracts in the blockchain network. Users interact with the smart contract via a web interface to create processes for collecting data from gateways in the sensor network. Th is blockchain-based system enhances the security of stored data queries and ensures the integrity of the shared data.