Market index is the spot price, and stock index futures is the expected price of the market. Although the market has fallen, it is not impossible for stock index futures to rise and the market to fall because people are optimistic about the future market trend.
Generally speaking, the shorter the contract term, the greater the probability of synchronization with the broader market. The final settlement of stock index futures is based on spot index. At present, there are only Shanghai and Shenzhen 300 stock index futures, so the final delivery depends on the specific point of the Shanghai and Shenzhen 300 index. Futures have a time limit. Within this time limit, people can expect to go up or down, which has time value. However, as the term approaches, the futures price will be closer to the spot price, and there will be differences between the futures price and the spot price.