In this paper, we first construct all indecomposable modules whose dimensions of weight spaces of the even and odd parts are ≤ 1, then classify all Harish-Chandra module over the super-Virasoro algebras, proving that every Harish-Chandra module over the super-Virasoro algebras is either a highest or lowest weight module, or else a module of the intermediate series. This result generalizes a theorem which was originally given as a conjecture by Kac on the Virasoro algebra.