One of the characteristics of futures trading is that it does not need physical delivery, and buyers and sellers can end their obligations through an opposite transaction before the contract expires, which is the "hedging" system. After the implementation of the "hedging" system, both parties to the futures contract can have two choices: one is to keep the contract until the agreed delivery date and then deliver it according to the conditions stipulated in the contract; Another option is to conduct the opposite transaction at any time before the contract expires, so as to achieve the purpose of "hedging" or "liquidation".