Abstract: A multi-objective nonlinear integer programming model was proposed to study the school bus problem.In the model,there are five objectives: to minimize the number of buses,to minimize total travel time of buses,to minimize total travel time spent by all children,to balance the loads among buses and to balance the travel time among buses,the objectives are sorted into four levels.A new heuristic optimization algorithm for solving the problem was presented.The algorithm starts with generating a minimum spanning tree to find basic routes,and then selects an adjustable unit to modify and determine the final routes.Further adjustment on the routes after the routes have been set is allowable if it follows some presented rules.