Most of the scheduling algorithm of elevator group system today mainly focus on how to reduce the waiting time of pessengers and running time of elevators, and the energy consume of elevators is always ignored. a least-cost energy dispatching algorithm for elevator group system based on ancolony algorithm is proposed in this paper. because the the dispatching problem of elevator group control system is a sypical combinatorial optimization problem, and the antcolony algorithm is good at solving discrete commbinatorial optimization problem, and it has good global optimization ability and fas convergence ability. in order to achieve the goal of energy saving, first the algorithm model and the energy objective function established; second, optimal convergence mechanism based on pheromone-update and the elevator-select probability is proposed; and tabu list used. finally, data simulation experiment was taken and the result of data simulation show that the algorithm is efficient and effective.