In this paper, trajectory tracking control problem of an unmanned surface vehicle (USV) suffering from complex environmental disturbances is solved by designing a fixed-time trajectory tracking controller (FTTC), in which the finite-time exact disturbance observer (FEDO) and fixed-time fast sliding mode (FFSM) controller are devised. The excellent features of FTTC strategy are as follows. On the one hand, by combining terminal sliding mode technology with fixed-time theory, the FFSM controller is designed for achieving stable trajectory tracking within a fixed time. In particular, the fixed time could be explicitly given irrelevant to system initial states. On the other hand, the FEDO is deployed to rapidly estimate disturbances arisen from complex environments. Finally, both feasibility and superiority of FTTC scheme are demonstrated by numerical simulations and comparisons.