Abstract: Vacuum system is the basic guaranteed system for the safe and stable operation of the EAST fully superconducting Tokamak device. Vacuum leakage will affect the plasma discharge and cause serious damage to the vacuum equipment. With the gradual upgrade of EAST, the vacuum system has become more complex, and the equipment is gradually aging, and the risk of leakage will increase year by year. The vacuum pumping system, vacuum measurement station, and real-time leakage rate monitoring system in EAST are introduced. Based on the pressure change data of the vacuum chamber, the leakage rate of the inner vacuum chamber was analyzed using the static pressure rise method, and the overall leakage rate of the inner vacuum chamber before plasma discharge was calculated to be about 2.2×10⁻⁴ Pa·m³/s. Based on the data of vacuum degree and residual gas composition during leakage failures over the years, analysis was conducted on different types of leaks in the vacuum chamber of the EAST device during various stages of operation. The study found that the different leakage location, leakage medium, and wall conditions resulted in significant differences in residual gas composition characteristics. According to the characteristics of the leakage, different leakage treatment methods were adopted. This study provides reference for timely and accurate identification and handling of leakage locations in the vacuum chambers of EAST and future fusion reactors.