The risk of stock investment has obvious duality, that is, its existence is objective, absolute, subjective and relative; It is both inevitable and controllable. Investors' control of stock risk is aimed at the duality of risk and adopts a series of investment strategies and technical means to minimize the cost of risk. Human's understanding of the operating logic of the stock market is a challenging world-class problem, which is also the root of the stock investment risk. So far, there is no convincing theory and method that can stand the test of time, and almost no method can accurately predict the trend of stock market and bond market in the next few days or weeks, but it is possible to predict the price for more than three years through research.