High efficiency environmental protection air-air cooled generator can be widely used in regions with poor ambient air quality such as the chemical plant, thermal power plant, and runs stably in the long time, which solves the problem that traditional generator can not used for long periods under complex and bad circumstance. The protection class is raised to IP55 while ensuring generator’s performance, which protects generator internal structure from harmful substance corrosion in air, and prolongs the life of generator and meets user's requirement.