What are the explanations for the compulsory lightening system of stock index futures? When there is a continuous one-way market in the same direction, the compulsory lightening measure is an effective measure to resolve the market risk, and this system has played an important role in the smooth operation of the domestic futures market. Some investors have various trading risks because they are not prepared enough for compulsory lightening measures. Here, investors are reminded to pay attention to the following points: loss positions need to meet certain conditions before they can participate in forced lightening. Customers should note that not all loss-making positions will be automatically forced to lighten their positions when they are forced to lighten their positions. If the loss-making position wants to participate in the compulsory lightening, investors need to take the initiative to declare the liquidation, and the position loss should reach a certain level. Investors should pay attention to the risks that may be brought about by compulsory lightening, and the risks brought about by profitable positions participating in compulsory lightening. In practice, profit positions are distinguished only according to the size of profit, but not speculative positions or hedging or arbitrage positions. The risk that hedging and arbitrage positions may be forced to reduce their positions.