This paper investigates the battery charging schedule problem of a battery-swapping station for electric buses (EB). An EB assignment policy is proposed such that there is a one-to-one correlation between EBs and batteries. By this means, the battery charging schedule problem aiming to minimize the total cost of the battery-swapping station is formulated as a constrained convex program with both spatially and temporally coupled constraints. Based on dual decomposition and our proposed EB assignment policy, the battery charging schedule problem can be decomposed into a series of local subproblems, which can be independently tackled. Furthermore, a fast search method in combination with binary search is put forward to deal with subproblems. Therefore, the battery charging schedule problem can be solved efficiently in a distributed manner. Numerical results confirm the validity of our proposed approach.