Algorithmic stablecoin is a method to adjust the total amount of money in the market according to the algorithm, increase the market supply when the stablecoin price is higher than the anchor price, and recover the supply when the stablecoin price is lower than the anchor price, or balance the stablecoin price by providing arbitrage space. The establishment of this model does not anchor real legal currency or pledge stable currency, but is regulated by the will and algorithm of the market, which is also known as flexible currency. The demand and potential value behind algorithmic staboin lies in how DeFi can achieve low collateral rate or even no collateral step by step, and ultimately change the money supply entirely by automated algorithms. The first-generation algorithm stablecoin AMPL is a typical single-currency system. After AMPL, the algorithm stablecoin represented by ESD soon appeared, which introduced the game mode of bonds and transferred the volatility to bonds. Without breaking away from the single currency model, stablecoin's algorithm and anchor assets have been adjusted, and it has entered the stage of "simulated Federal Reserve bond issuance". The emergence of Basis allows the community to enter the "multi-currency mode" of algorithm-based stable currency. Basis imitates the modern central bank regulation system of base money supply and issues Basis Cash (BAC), Basis Bond (BAB) and Basis Share (BAS) tokens. These three tokens correspond to dollars, bonds and stocks, adding richness to the system. Compared with the first-generation algorithm stablecoin, the multi-currency mode aims to increase the stability of the system. The design was once highly regarded by the community. But Basis has fallen since its launch in January and is now down to $0.08, far from achieving its goal of algorithm-stability, and the community has raised questions about the relationship between the models. Frax has been described as the next generation of algorithmic stablecoin. The model starts with a "mimic central bank" approach. Similar to Basis Cash, Frax proposed three tokens -- Frax Shares, Frax Bonds -- but to mint a Frax token, Users must deposit some combination of Frax Shares (FXS) and other collateral (USDC or USDT) worth a total of $1. According to statistics, this model introduces some mortgage assets, and the algorithm dynamically adjusts the details of the model to improve the stability of the whole system. UST and FRAX showed the lowest volatility in TokenInsight's Q2 DeFi industry report, with an average deviation of less than 0.2%. In the market, the problem of algorithmic stablecoin also emerged one after another, ESD and BAC anchored at $1, but completely broke away from the anchoring in the second quarter; AMPL, which has always been pegged to the exchange rate, has become the most volatile of the major algorithmic stablecoins. On the positive side, FRAX is very stable at $1 over a long period of time, and the arbitrage mechanism has helped FRAX to achieve price anchoring effectively, with very few positive or negative premiums above 1%. So far, algorithmic staboin projects have been based on the mortgage model of digital currency, with various innovations around the mortgage rate, from ESD of zero mortgage, to FRAX of dynamic mortgage, and the subsequent FEI of overmortgage. These attempts strike a difficult balance between mortgage rates and risk. In addition, the newer stablecoins FLOAT and RAI, which start with the golden ratio of 1.618 and are also considered a low-volatility currency, do not choose to anchor the DOLLAR. This also shows that there may be new opportunities for non-DOLLAR stablecoins, and algorithm stablecoins are still in the stage of trial and exploration. How to balance and play the game between "market size" and "price stability" of algorithmic stable currency is the biggest hotspot of the market and community for algorithmic stable currency. Up to now, the idea of each project is becoming more conservative. What the market and the community need more is the "stability" of the algorithm stablesoin. DeFi has shown great charm in the first two of the three major sectors of "lending, mortgage and stablesoin". The development of stablesoin is still regarded as a great space, and the market still has too much expectation for "decentralized stablesoin".