Abstract: The crescent spring lakes are the small lakes in the desert due to uprising of the ground water table and gushing water from the depressions between sand dunes. There are several thousands of the crescent spring lakes in the Huangheyuan desert, which are important for improving the ecology of the Yellow River source. The authors studied the formation and mechanisms of the crescent spring lakes through field investigations and the remote sensing interpretation from 2011 to 2014. The Huangheyuan desert develops on the old Yellow River bed on the Qinhai-Tibet Plateau. The sediment deposit underneath the ground surface consists of gravel and sand, thus the ground water may flow through the interstices between the particles for several tens of kilometers and provide water to the crescent spring lakes. Climate change and increased precipitation have resulted in uprising of the ground water and formation of many crescent spring lakes in the past decades. The impoundment of the Huangheyuan dam reservoir raised the water level in the Erling Lake to 4 273 m in 2002. Consequently, the ground water table in the Huangheyuan desert was suddenly raised by 20 m and the distribution of the crescent spring lakes extended from 30 km to 50 km from the Erling Lake. The number of the crescent spring lakes increased by 3 times and the total water surface of the crescent spring lakes in the desert was doubled. The new crescent spring lakes are not stable and may move with sand dunes for a distance of 3~13 m a year. If the crescent spring lakes receive water supply for more than a decade, the herbaceous vegetation develops on the sand dunes, the surface sand is weathered and the sediment particles become finer, the desert will be stabilized and become a greenland.