A method for audio-video synchronization in a virtual reality (VR) system is provided. The VR system includes a VR device and a host device. The method includes the steps of: connecting the VR device to a host device via a data transmission interface; transmitting an audio signal and a video signal from the host device to the VR device; estimating time delay information in an audio transmission path and a video transmission path of the VR device; transmitting a feedback signal recording the time delay information from the VR device to the host device; and adjusting timing of the audio signal or the video signal transmitted from the host device to the VR device according to the feedback signal.