Hazel is an oracle machine which intends to make the on-chain information comply with the off-chain one. It is the foundation to have on-chain information always kept pace with off-chain information and to make money by arbitrage. In terms of its function of achieving arbitrage for users, the quotation provided by the oracle machine will be tightened to the market price by means of arbitrage mechanism. Because of the unsound pricing mechanism, there are always opportunities for making arbitrage in the trading market, thus attracting arbitragers to invest their money in the project all the time. Driven by arbitragers’ manipulation, the pricing mechanism will be corrected and the DeFi market together with its corresponding products will tend to be more excellent. In such a circulation, the DeFi will continue to thrive.