Researches were performed to reveal the overall development trend of south Qiangtang area by extracting multi-temporal TUPU using interpretation results of several remote sensing images from 1992 to 2005. The results of TUPU deriving reveal that there has been a sharp augment in lake area extension of the study area—Namco watershed of south Qiangtang—during the past 15 years. The typical lake was used to analyze some specific variation features, and the steadily increased area was extracted as well. Based on analyzing the variation information from multi-temporal TUPU together with the meteorological data, the authors used some factors to interpret the rapid extension of lakes in Qinghai-Tibet Plateau, such as the average annual precipitation, which could affect the increase of lake areas indirectly by reacting on the movement of glaciers.