For the formation control problem of time-varying topology multi-agent systems with resource-constraints, an event-triggered mechanism based on combination error information is presented to reduce the unnecessary information transmission and lower the occupation of bandwidth, and the formation control protocol and distributed event-triggered mechanism are designed for multi-agent systems. By transforming the formation control problem of multi-agent systems into the stability problem of closed-loop time delay system, the Lyapunov-Krasovskii functional is constructed, and the sufficient condition of formation is provided by using linear matrix inequality(LMI) techniques. Finally, a simulation example illustrates the effectiveness of the proposed method.