An environment monitoring system, and particularly an unmanned aerial vehicle environment monitoring system and monitoring method. The unmanned aerial environment monitoring system comprises a flight control module, a navigation module, a data acquisition module, an environment detection module, an optical camera, a barometric altimeter, a memory and a wireless transmission module mounted on an unmanned aerial vehicle, and a ground work station. The data acquisition module is connected to the environment detection module, and is further connected to a GPS, the barometric altimeter and the memory. The optical camera stores images in the memory. The wireless transmission module is connected to the ground work station via a wireless communication network. The ground work station controls the unmanned aerial vehicle, receives environmental data, geographical data and image data, and performs storage and analysis processes. The monitoring system achieves a fast, comprehensive and accurate monitoring function for an environmentally protected monitoring region, enhancing monitoring efficiency as well as monitoring instancy and intuitiveness.