Abstract: The module high-temperature gas-cooled reactor (HTGR) is an advanced reactor with high safety and high efficiency in electric power generation. The steam generator heat-exchange tube rupture accident which will result in the water ingress to the primary circuit of reactor is an important and particular accident, and it may result in chemical reaction of graphite fuel and structure with water causing severe results with massive release of radioactive isotopes and production of explosive gaseous in large quantity. The analysis of the water ingress accident is significant for verifying the inherent safety characteristics of HTGR. The seriousness of the accident consequence is affected directly by the amount of water ingress mass. The 10 MW High-Temperature Gas-Cooled Reactor (HTR-10) designed by the Institute of Nuclear and New Energy Technology of Tsinghua University was selected as an example of analysis, and the 2-area (2A) broken (or double-ended breakup) single and two heat-exchange tubes at the inlet and outlet of steam generator were simulated respectively by RETRAN-02, a general-purpose thermal-hydraulic system analysis program. The amount of water ingress mass is related with the broken position, the broken area and the number of broken tubes. The amount of water ingress mass at inlet of steam generator is more than that at outlet. The greater the broken area or the number of broken tubes, the larger is the amount of water ingress mass. The water in steam generator could be drained effectively by the HTR-10 emptier system, so it will prevent the primary circuit of reactor from water ingress due to water leakage from steam generator.