Article in English: Beta is the risk, relative to the stock market as a whole, an investor assumes by owning a particular stock. That's why you need to compare the returns of a single stock against the returns of an index. The index is the benchmark against which the stock is judged. The risk of an index is fixed at 1. A beta of lower than 1 means that the stock is less risky than the index to which it's being compared. A beta of higher than 1 means the stock is more risky than the index to which it's being compared.  Take this example: Say that the beta of Gino's Germ Exterminator is calculated at .5. Compared to the S&P 500, the benchmark to which Gino's is being compared, it's half as risky. If the S&P moves down 10%, Gino's stock price will tend to fall only 5%. As another example, imagine that Frank's Funeral Service has a beta of 1.5 when compared to the S&P. If the S&P falls 10%, expect Frank's stock price to fall more than the S&P, or about 15%. High risk, high reward; low risk, low reward. A stock with a low beta won't lose as much as the S&P when it falls, but it won't gain as much as the S&P when it posts gains. On the other hand, a stock with a beta over 1 will lose more than the S&P when it falls but will also gain more than the S&P when it posts a gain.  For example, pretend Vermeer's Venom Extraction has a beta of .5. When the stock market jumps 30%, Vermeer's only gains 15%. But when the stock market sheds 30%, Vermeer's drops only 15%. If you make your beta calculations and find out the stock you're analyzing has a beta of 1, it won't be any more or less risky than the index you used as a benchmark. The market goes up 2%, your stock goes up 2%; the market goes down 8%, your stock goes down 8%. A good mix of high- and low-beta stocks will help you weather any dramatic downturns that the market happens to take. Of course, because low-beta stocks generally underperform the stock market as a whole during a bull market, a good mix of betas will also mean you won't experience the highest of the highs when times are...

Summary in Chinese:
掌握如何解释 Beta 系数。 理解风险与收益密切相关。 Beta 系数为 1 的股票与整个市场同步涨跌。 在您的资产组合中同时添加具备较高 Beta 系数和较低 Beta 系数的股票以分散风险。 类似于其他大多数金融预测工具，Beta 系数也不能准确预测未来。