MEMS devices usually have micro actuators contained in a cavity, If the pressure level of testing chamber is higher than that of cavity, moisture will ingress into the cavity, which may cause critical failure such as stiction of the moving parts. To design an accelerated life test based on high temperature and high humidity, such a phenomena should be considered. In this study, a throughput model that can estimate the amount of moisture ingress is used to decide the testing time and conditions of a high temperature and high humidify test.