The main research focus of this study is the collaborative optimization of mixed-operation bus departure intervals and vehicle utilization plans, involving both fuel-powered and electric buses. The optimization objectives are to achieve smooth departure intervals and minimize overall operational costs. Multiple constraints are considered, including departure interval range, number of vehicles, vehicle connectivity, and electric bus range. An optimization model is established to address these aspects. A genetic algorithm is designed to solve the two-stage model, enhancing efficiency and accuracy of the solution. The case demonstrate that compared to the existing operating scheme, this optimization model can allocate the number of buses used more reasonably with a relatively uniform departure interval. It achieves off-peak charging for electric buses, enhances vehicle utilization, and saves up to 13.04% of the total operational cost of vehicles.