A graph is said to be determined by its Laplacian spectrum, if there is no other non-isomorphic graph with the same Laplacian spectrum.Three types of bicyclic bipartite graphs H(n;n₁), H(n;n₁, n₂) and B(n;n₁, n₂), which all have the base of B(P₃, P₃, P₃) (three disjoint paths of length 2 between two vertices) were studlied.It is proved that the graphs are determined by their Laplacian spectrum, and the graphs obtained by the join of complete graphs and the above three type bicyclic graphs are also determined by their Laplacian spectrum.