Containment is the last physical barrier for nuclear power plant to prevent the escape of radioactive materials, and the containment tightness is an important index for the evaluation of containment performance. Accurate and effective containment evaluation is crucial for nuclear safety of nuclear power plant. This paper uses CFD numerical simulation calculation method to simulate the leakage rate test process, analyzes the influence of leakage location, leakage port size and other factors on the temperature field in the shell, studies the influence of the selection of pressure measurement points at different heights on the calculation of leakage rate, and aims at the non-adiabatic containment under the influence of external environment. The leakage rate values obtained by weighted method, volumetric average method and finite element analysis are compared and analyzed, and the quantitative error of leakage rate calculation by finite measuring points is evaluated. The results show that within the permissible range of containment leakage rate, the leakage location and the size of the leakage port have little influence on the temperature field in the containment. The difference of pressure measurement points in the height direction has a certain effect on the calculated value of dry air quality in the shell, but has little effect on the calculated value of leakage rate. Even if there is no internal heat source in the containment, the deviation value of leakage rate calculated by using finite temperature measuring points will increase significantly if it is greatly affected by the change of external environment temperature.