Abstract: To resolve the reliability sensitivity analysis problems of unknown limit state function,a reliability sensitivity analysis method that uses response surface method(RSM) to get the ultimate state function for reliability sensitivity analysis was proposed,and the correlative formulas were deduced.The randomness of the flux and temperature of the lubricant at accessory gearbox inlet,and that of the temperature and velocity of the airflow outside accessory gearbox were considered;and the reliability of accessory gearbox outlet temperature and the reliability sensitivity of various random variables were calculated by the method of this paper.The result is consistent to references,showing that the method of reliability sensitivity analysis and the correlative formulas are correct and efficient.The method provides quantitative theoretical warranties for the reliability design and optimization of correlative accessories and accessory gearbox itself.