This paper presents a sliding mode formation control strategy for multiple unmanned surface vehicles (USVs) subject to quantized communication. On the sensor side of each follower USV, a velocity observer is constructed, and then an event-triggering mechanism is designed to sample the output of the observer. The quantized values of the sampled states are sent to the network to further reduce communication costs. In addition, each USV receives the event-triggered and quantized information from its neighbors through a communication network. A sliding mode formation control protocol is developed for follower USVs to handle parameter uncertainties, measurement errors, and quantization errors. The formation tracking error can converge to a small vicinity of zero. The simulation results verify the effectiveness of the proposed control scheme.