The stablecoins is stable, because the issuing process needs a full backup of a fiat currency; it is private, because unlike the fiat currency, it is not supervised by the national organs but the issuer alone; it is convenient, because it’s faster than those payment tools without the blockchain technology; but the utmost important one of all these characteristics is, half-centralized. The main object of this study is to know the basic characteristics of the stablecoins and show clearly to readers what the stablecoins (and their issuers) are, and what they could do to the modern world.