The continuity of the main force in futures is connected by the K-line of the contract with the largest trading volume among all contracts of this variety, mainly to avoid the price discontinuity caused by the change of the main force in the current month and to facilitate investors to study the long-term price trend.

Because the main contract is the contract with the largest volume, which contract has the largest volume, the K-line on the futures is the K-line chart of this contract.

For example, it's April, and if the XX 1407 contract has the largest transaction volume now, the continuous chart shows the K line of the July contract. May and August have the largest contract turnover, so the continuous chart shows the K-line chart in August. And so on.