It is necessary for the selection of integral cross section to consider the significant influence of micropore area density（the ratio of micropore area to calculation domain area）to cavitation and hydrodynamic effect in the process of the leakage calculation for the mechanical seal with micropores.Based on the massconservative JFO cavitation boundary condition,a numerical calculation model was developed.The influence of micropore area density on calculation of mechanical seal leakage was discussed.The simulation experiment results show that there is a limit to the integration method based on the laminar flow in the calculation of the leakage of mechanical seals with micropore,and it is not suitable for all the micropore area ratios.The integral section can not be found when the micropore area ratio is greater than a certain value.With the analysis of cavitation and hydrodynamic effect by the investigation of the plots of the flow distribution along radial direction,it can be found if the reasonable integral cross section exists in the seal with different micropore area density.