Abstract: By taking leak mode of liquid tank as the research object and setting leaking pressure as invariant, liquid model is built. The relationship between leak time and leakage volume, mass rate and liquid height are analyzed by simulation leak process in cylindrical vertical tank. The results show that decreasing liquid height, increasing leakage volume and decreasing mass rate are found with prolonged time at one hole mode, and the change rate of the leakage volume, mass rate and liquid height are decreased. Test value of leakage volume and mass rate are near to theory calculated ones. The leakage volume from one hole and two holes at the same time are nearly equal when the leak areas are the same. The research results offer scientific basis for emergency aid and consequence quantitative analysis of dangerous liquid tank leakage accident.