In order to solve the relay tracking problem of remote sensing constellation for multiple time-sensitive targets, this paper constructs a mega low orbit remote sensing constellation based on the Walker constellation design principle. The constellation can not only achieve continuous coverage of ground targets in time and space, but also regularly return to the initial ground trajectory as a whole. For non-cooperative time-sensitive targets, the constellation adopts a target pre-allocation mechanism to transmit target information to neighboring satellites with access potential, reducing constellation communication costs. Subsequently, dynamic priority is assigned to the target, and the priority is adjusted in real-time based on the planning results, so that the constellation can ensure observation of high priority targets and alleviate observation conflicts with neighboring targets. Finally, a coverage regression constellation with the minimum number of satellites is constructed in the simulation analysis, and the constellation is used to achieve continuous tracking and observation of multiple time-sensitive targets.