Abstract: Abstract: The Source Region of Three Rivers is the cradle of China's Yangtze River, Yellow River and Lancang River. It is also a national wetland, a region with biodiversity and ecological fragility. With the economic development and environmental deterioration, the shortage of freshwater resource has become the important obstacle of economic construction and ecological restoration. Development and utilization of freshwater resource in the atmosphere is one of the main ways to solve the shortage of freshwater source on the ground surface. The implementation of artificial enhancement precipitation is an effective mean to the development of cloud water resource in complex weather conditions. The conventional manned aircraft, rocket and artillery operations cannot carry out scientific cloud seeding implementation into complex weather operation field because of some safety and airspace restriction issues, however, unmanned aircraft is a valuable tool to control and recover in meteorological survey and cloud seeding, and it is also an important direction of key technology of equipment research and development in weather modification. It is imperative that the developed unmanned aircraft, which is suitable for the characteristics of the plateau weather, adverse climate and complex terrain, is detectable, operable, controllable and recyclable, and has long voyage and high payload in enhancement precipitation. In the study, the unmanned aircraft of LY-Z200 prototype was employed as the embryonic form; through changing its mode of landing and takeoff, adjusting the engine power and position, and installing the deicer, the flying height and safety were improved. After the installment of sensors of conventional atmospheric detection, small cloud seeding instrument, and aerial photography equipment, the unmanned aircraft was developed completely, which was LY-ZY200 prototype suitable for plateau enhancement precipitation. Using this unmanned aircraft, 4 modification tests showed that the engine power of unmanned aircraft was affected by hypoxia in a high altitude, the flying height was decreased, the takeoff distance was lengthened, and the height of climbing was lowered. Accordingly, the LIMBACH-L550 electric field intensity engine with 31 kW was used to improve the climbing height, and the results displayed that the flight height was up to 6 100 m, the takeoff weight was 171 kg, the payload was 50 kg, the oil volume was 42 L the maximum fuel consumption was 7.2 L/h, the cruising speed was up to 187.2 km/h, and the cruising time was up to 4 h. These indications satisfied the diverse requirements to implement a wide range of the enhancement precipitation task and the loading in the plateau field. The deicing device was installed and the propeller to resist hail was upgraded in the unmanned aircraft to ensure it could normally operate in -4 ℃ low-temperature cloud field safely and efficiently. The installed sensors of atmospheric temperature, humidity and pressure and the designed small-scale enhancement precipitation seeding device could ensure to carry 10 catalytic lobes and perform scientific operations in appropriate seeding fields. Upgraded flight control and mission systems could achieve information exchange and diverse mission requirements between unmanned aircraft and ground terminal. Using the LY-ZY200 prototype in plateau complex weather conditions, the typical enhancement precipitation test results showed that the unmanned aircraft could pass through the thick cloudy and the complex environment in cloud, achieve a stable, planning and seeding flight, and obviously reflect the effects of enhancement precipitation in cloud seeding on the ground. Consequently, the unmanned aircraft opens an ideal operation mode and provides a detection tool for enhancement precipitation at proper position, time and amount.