In this paper, a novel event-based distributed control scheme is proposed to address the coordinated control problem for multiple spacecraft formation flying, in the presence of mass uncertainties and external disturbances. Considering that the on-board resources in terms of communication and computation are limited, the event-triggered mechanism is applied to regulate the information transmission frequency among formation spacecraft and to govern the update time of the controllers. In doing so, each spacecraft only needs to broadcast information and update its own control command when the specified events occur, thus relaxing the communication network burden and saving on-board resources. Moreover, the inter-event time intervals are shown to be strictly positive so that no Zeno behavior executes. By Lyapunov's stability theorem and topology theory, it is proved that the formation-keeping maneuvers are globally asymptotically achieved. Finally, simulation results are presented to show the effectiveness of the proposed control scheme.