This paper investigates the problem of distributed dynamic event-triggered formation control for multiple unmanned surface vehicles (USVs) subject to external disturbances. Firstly, a novel event-based distributed formation control scheme is proposed, under an undirected communication graph. Wherein, a dynamic event-triggered data transmission mechanism is designed for communication resource reduction. The time-varying dynamic parameter ensures fewer triggering instants and a larger triggering time interval compared with the traditional static one. The adaptive laws are incorporated into the formation control scheme to address the effects of external disturbances and uncertainties. Subsequent to the theoretical analysis, it can be concluded that the relative tracking errors can converge to the origin, and all closed-loop signals are bounded. Moreover, it is proved that the triggering time sequences do not exhibit Zeno behavior. Finally, a numerical simulation is performed to verify the effectiveness of the proposed distributed formation controller.