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In this paper, a formula of the Laplacian and signless Laplacian spectrum of semi-Cayley graphs over abelian groups is given. As applications of our main result, special formulae of Laplacian and signless Laplacian spectrum are also given for two classes of semi-Cayley graphs (one matching bi-Cayley graphs and the join of two Cayley graphs over isomorphic abelian groups). In particular, a method to construct Laplacian and signless Laplacian integral semi-Cayley graphs is obtained.