Given a finite group G, the genus spetrum \(\textrm{sp}(G)\) of G is the set of integers \(g\ge 0\) such that G can act faithfully on an orientable closed surface of genus g by orientation-preserving homeomorphisms. The determination of \(\textrm{sp}(G)\) is a classical topic and has a long history, but progress is lacked. In this paper, when G is an abelian p-group with \(p>2\) , we propose a new approach to \(\textrm{sp}(G)\) , giving a structural description for \(\textrm{sp}(G)\) in terms of a function which can be computed in finitely many steps.