The reliability of a hierarchical incentive system was determined by its subsystem components and the relations among them. measures The responsiveness of incentive system reliability to the probability changes of effectiveness on incentive level was measured by the sensitivity of incentive system reliability.  Mathematical model indicates that the level of incentive and incentive path dependence are two vital influential factors to incentive system reliability. Two approaches for firm to improve the incentive system reliability are optimal allocating the limited incentive resources to the top incentive which can produce largest incremental effect，and improving dependence between upper and lower levels.