In this paper, we design DeLottery, a decentralized lottery and gambling system based on block chain technology and smart contracts. Lottery is a classical form of entertainment and charity for centuries. Facing the bottleneck of the combination between lottery and information technology, we use smart contracts and blockchain in decentralized, intelligent, and secure systems for lottery industries. Moreover, we are inspired by the algorithm of RANDAO, an outstanding way of random number generation in blockchain scenario. The components and the functions of the novel system are described in details. We implement DeLottery in a blockchain network and show functioning procedure and security of the proposed lottery system. CCS Concepts• Applied computing~Secur e online tr ansactions; Electronic funds transfer • Information systems~Secure online transactions Keywor ds lottery system, decentralized, blockchain, smart contract