2020 has seen the great flourish of the automated market maker（AMM） based decentralized exchanges（DEX） on public block chains. Dozens of different automated market maker trading mechanisms are proposed and tested in real production environment，and this trend is unlikely to be discontinued in the near future. With the help of AMM，DEX has grown up to be a comparative force with traditional centralized exchanges（CEX）. AMM exhibits different features with traditional order driven market and quote driven market. Its emergence refreshes our cognition to the financial market，and gives us more options to organize the market. As a trading mechanism，AMM can not only be utilized by a decentralized market，but also can be utilized in a centralized market. This article serves as a brief review to the development of AMM trading mechanism.