As the world's biggest energy consumer and the world's first car production and marketing country, car exhaust emissions have become an important cause of serious environmental pollution. The paper calculates the life cycle costs of HEB, BEB, and CDB by the life cycle cost model considering the environmental benefits in the case of small public transportation system being the big scenarios. The paper takes the capital airport shuttle bus system as an example, analyzing applications of alternative energy in the system, thus providing evidence for applications of alternative energy in a small public transportation system, improving continuously the proportion of electric energy in the consumption of end-use energy, promoting social energy conservation and mitigating environmental pollution problems.