There are four contracts to be traded at the same time, namely the current main contract, the main contract next month and the third contract in the next two quarters. For example, now the main contract is 1 1 month, then the main contract is 1 1 month and1February. That is, if111,if112, IF 1203 and IF 1206. IF index is the weighted price of these four contracts based on the position weight. For example, the total position today is 4 1422 lots, and the four contracts each account for 3 1678 lots, 7,607 lots, 1726 lots and 41/kloc-0 lots. The IF index can be calculated by averaging with the price.