1 The futures and spot prices of the same or similar stock index varieties are more similar, and the price consistency of the futures contract maturity date is also stronger. Therefore, when investors hedge, the futures varieties they choose are the same as or as close as possible to the spot varieties to be hedged.

Investors in opposite directions must trade in opposite directions in the spot market and the futures market when implementing hedging operations. Because the same (similar) commodity has the same price trend in two markets, it is bound to make a profit in one market and lose money in the other market, thus achieving the purpose of maintaining value.

3 Principle of Scale Equivalence Theoretically, when hedging, the value of the stock portfolio to be hedged should be equal to the value of the stock index futures contracts bought and sold in the futures market, so that the profit in one market is equal to the loss in another market. However, in the specific operation of hedging, the concept of hedging ratio is introduced when determining the number of futures contracts, and the optimal hedging ratio is calculated according to the corresponding hedging model, thus determining the value of futures contracts in hedging.