Fuse means that when the stock price fluctuates to a certain extent, the transaction will be suspended or terminated. Recently, the American stock market has been blown five times in a month, which shows that the American stock market fluctuates greatly. Recently, American stocks have been blown frequently, and the epidemic is only the fuse. The most fundamental reason lies in the trading system of US stocks and the long-term inflated asset prices. An analysis of the reasons why US stocks are blown so frequently: there is no limit to the ups and downs of US stocks, that is to say, the fluctuations of US stocks will be unrestricted in an emergency, which will also induce market sentiment to be released within one day, rather than in the long run. Second, the leverage ratio of the US stock market is relatively large. Many institutional traders in the United States trade through leverage, which will undoubtedly cause the stock market price to be artificially high and aggravate the fluctuation of the financial market. Third, the financial derivatives market in the United States is very large, especially the stock index futures and options market. When the market is unfavorable, the derivatives market will be sharply shorted, and the financial derivatives market has the function of price discovery, which will naturally aggravate the fluctuation of the financial spot market. Fourth, asset prices in the United States are artificially high, with a price-earnings ratio of 20 19 of 27.7 times. 1872 by 2000, the average P/E ratio of US stocks was 7 times during the bear market and 22 times during the bull market. The current price-earnings ratio is too high, indicating that there is no performance support behind the stock price, and the stock price is inflated. These are the reasons why American stocks have been blown frequently recently. At present, the fluctuation of the American stock market is still very large, and investors need to be prepared to guard against risks.