Abstract: In order to explore the scale of urban development and its changes, and solve the problem that a single indicator cannot fully characterize the size of cities and towns, the comprehensive rank-scale law is used to study the characteristics of urban size distribution and its changes in Guizhou Province from 2000 to 2015. The results show that: From 2000 to 2015, the scale of Guizhou cities and towns followed the rank-scale law, the concentration distribution index q value was between 1.072 49-1.137 56, which approached the rank-scale ideal value 1. The order of the towns in the middle has changed drastically, and the order of the towns at both ends has hardly changed, showing a monofractal characteristic as a whole. Spatially, it presents a gradient distribution pattern in which cities and towns in the west, north and northwest are ranked high, while those in the east and south are low.The size of Guiyang which is the capital of Guizhou Province, has always been the first, but the urban primacy index is less than 1.3. The ratio of the size of Guiyang to the last towns has dropped from 32.09 times in 2000 to 6.35 times in 2015. The comprehensive rank-scale law can effectively describe the scale of Guizhou cities and towns.The leading role of the first town in Guizhou needs to be further enhanced.