Liquidity risk can be divided into two types: one can be called liquidity risk; Another can be called amount risk. Liquidity risk refers to the risk that futures contracts can't be established or closed at a reasonable price in time, which is easy to happen when the market situation goes to an extreme sharply or when you want to deal with assets but can't get what you want because of a special transaction. The liquidity of stock index futures market is usually measured by the breadth and depth of the market. Breadth refers to the ability to meet the trading needs of investors at a given price level. If both buyers and sellers can get the required trading volume at a given price level, then this market is breadth. If both buyers and sellers are limited by trading volume at a given price level, then the market is narrow. Depth refers to the market's ability to accept the demand of block trading. If a small amount of extra demand can greatly increase the price, then the market lacks depth; If a large amount of additional demand does not have a big impact on the price, then this market is deep. The market with higher liquidity has higher stability and more reasonable market price. The risk of capital amount refers to the risk that an investor's position will be forced to close when his capital cannot meet the margin requirements.