The gas leakage of the steam turbine condenser is affected by many factors

and it is difficult to calculate quantitatively in actual operation. This paper proves a less-known and less-used but HEI recommended formula through analysis of the fundamental principle of leakage. At the same time

the main influence factors were analyzed and modified calculated

in order to establish a direct mathematical relationship between the amount of air leakage and the vacuum drop rate which is easy to gain and customary using by professional personnel. This paper makes it apply to the condenser variable conditions.