As important type of reasoning besides induction and deduction, abduction has been widely used in many areas, such as AI. Generally speaking, abductive reasoning is the process of inferring causes from the observations. Unlike past research, which uses prime implicate and prime implicant, this study proves that seeking minimal interpretation of abductive problem for propositional logic and propositional modal logic system S5 can be reduced to the problem of seeking minimal hitting set in the corresponding set, and presents a new method for solving abductive problems.