It is a technical analysis index, which judges the long-short trend of the market by comparing the trend of market price and volume. According to public information, the calculation method of long-short index is complex, which requires mathematical formulas and statistical methods. There are two main types according to the price trend and volume. Indicators based on price trends judge long and short trends through market highs and lows; Based on the index of trading volume, we can judge the trend of long and short through buying and selling.