"Main contract" refers to the contract with the largest position and turnover in a month. This is the case with the agreed binding. When the position really moves up, there are often two contracts with large trading volume. And these two contracts sometimes "go up" or "go down". I often use this to trade on different contracts. In addition, cross-month arbitrage can also be carried out. The reason why people trade in the main contract is because the main contract has a large turnover, easy to clinch a deal, large fluctuation and easy to make a profit. Moreover, the main contract often differs from the current month by several months, which can be long-term or short-term. So there are main contracts and non-main contracts.

The "master contract" will change over time. After one delivery month, the main contract is transferred to the next delivery month. We will also move the warehouse in operation accordingly. Switch to the new main contract for operation. Therefore, the main contract does not refer to which contract, but should be understood as: "the most active contract."

In order to record historical prices, different market softwares use different compilation methods. The most representative ones are "continuous" and "exponential". For example, Master Boyi's "Shanghai Copper III" and "Shanghai Copper IV" refer to the prices of the third and fourth months from the current month. For example, the price of "Shanghai Copper Company III" is the current contract price11kloc-0/,while "Shanghai Copper Company IV" is the current contract price 1658. Over time, the following "Shanghai Copper Company III" and "Shanghai Copper Company IV" will become 1 102 and 1 103, and so on. In this case, if you look at the K-line of "Shanghai Copper Company", you will find that its trading volume is already relatively large, because often the main contract of copper is a contract that is three months from the spot monthly contract. In this way, the purpose of "recording the historical price of the main contract" has been achieved. It provides data for investors to analyze historical markets.

The other is the index compilation method, such as Wenhua Finance, which is based on the weighted average of the prices of various contracts with the volume as the weight. This method is also a way to record historical prices. In my personal experience, this method is more scientific. I have a trading rule: analyze with the index and trade with the main force. That is, analyze the trend, look at the index, operate, open the main position, set the stop loss and so on.