Legal analysis: In principle, it is the same as securities trading, and centralized computer bidding is conducted according to the principle of price priority and time priority. Trading orders, like securities, include market order, limit orders and cancellation order. Generally speaking, there are four stock index futures contracts within six months, namely the spot monthly contract of the current month, the monthly contract of the next month and the monthly contract of the last two quarters. With the monthly delivery, the contract will be pushed forward in a rolling way.

Legal basis: Article 2 of the Regulations on the Administration of Futures Trading. Any unit or individual engaged in futures trading and related activities shall abide by these regulations.

The term "futures trading" as mentioned in these Regulations refers to the trading activities in which futures contracts or options contracts are the trading targets by open centralized trading or other means approved by the the State Council Futures Regulatory Authority.

The term "futures contract" as mentioned in these Regulations refers to a standardized contract that is uniformly formulated by futures trading places and stipulates to deliver a certain amount of subject matter at a specific time and place in the future. Futures contracts include commodity futures contracts, financial futures contracts and other futures contracts.

The term option contract as mentioned in these Regulations refers to the standardized contract uniformly formulated by the futures exchange, which stipulates that the buyer has the right to buy or sell the agreed subject matter (including futures contracts) at a certain price in the future.