This paper presents GeoWatch to conduct the first large-scale measurement study of geoblocking practices towards China. Although prior studies have examined geoblocking in specific contexts as well as China's censorship, GeoWatch focuses on identifying which websites proactively block users from China. It employs advanced domain mining techniques and globally distributed vantage points to identify geoblocking websites, analyzing a total of 97.78 million domains worldwide and identifying 4.54 million geoblocking domains.