Karst soil, a new vocabulary, appeared currently in the study of karst rocky desertification governance. Through analyzing literatures on karst soil and combining with the information of 2 755 soil profiles in the Houzhai River Watershed in Puding County of Guizhou Province, the soil types and their differences were explored, the correct definition of karst soil was established, and the differences between karst soil and soil in karst region in pure carbonate rock area was distinguished. The results showed that there are three major soil groups in the Houzhai River Watershed: limestone soil, paddy soil and yellow soil, the limestone soil is mainly distributed in the areas above the altitude of 1 250 m, and increasing with the increase of altitude. Paddy soil and yellow soil are mainly distributed in areas below 1 350 m in altitude. Limestone soil is mainly distributed in the peaks and depressions in the east of the watershed and in the mountains in the middle and west of the watershed. Paddy soil is mainly distributed in the depressions in the east of the watershed and the west of the middle rivers, but the yellow soil is distributed irregularly in the watershed. There are great differences in the profile morphological characteristics in the three soil groups. The average pedon thickness of limestone soil (49.68 cm) is lower than those of paddy soil (84.33 cm) and yellow soil (85.54 cm), but the average gravel content of lime soil (7.94 g/kg) is much higher than those of paddy soil (4.28 g/kg) and yellow soil (4.54 g/kg); Soil thickness is negatively correlated with slope for the three soil groups, and the average slope was 18.92° for lime soil , 1.52° for paddy soil and 3.23° for yellow soil. According to the definition of karst, karst soil should be defined as a calcareous soil derived from karst rocks, not soils distributed in karst region. However, lots of literatures confound the definition of karst soil, so differentiating karst soil and soils in karst region is of great significance to the management of rocky desertification. Soil profile data from the Houzhai River Watersheds indicate that in the pure carbonate area there is not only calcareous soil but also other soil types. Therefore, soils in karst region contains karst soil and non-karst soil, karst soil should specifically be referred to calcareous soil derived from carbonate rocks. It can better distinguish karst soil and soils in karst region by correct understanding of soil basic properties, the relationship between soils and vegetation, and the relationship between soils and parent rocks.