Surface acoustic wave-driven on-chip integrated acousto-optic modulators have become the critical technique in microwave-to-optical conversion due to their small footprint, high efficiency, low power consumption, and easy integration. In this paper, we summarize the recent progress of thin-film lithium niobate (TFLN) acousto-optic modulators, and mainly focus on their applications in microwave photon information processing. First, we introduce the basic principles of the TFLN acoustic-optic modulators. Then, we review the key research achievements in recent years, including the improvement and optimization of performance parameters such as modulation speed, modulation efficiency, and optomechanical coupling rate. Lastly, we discuss the potential applications of TFLN acousto-optic modulators with respect to the filter, frequency shifter, LiDAR, optical isolator, and microwave-optical conversion. The development trends of the TFLN acousto-optic modulators in the future are also briefly provided.