Land degradation is not only a great environmental problem at present, but a great economic and social problem. Land degradation in southwest China is mainly formed by water erosion. This paper, briefly descibed the land degradation status (slight, moderate and severe degraded land area is respectively 188852.5, 48128.81 and 16.393.62 km², and respectively makes up 14.30%,3.50% and 1.10% of the total area of southwest China)in southwest China, analyzed different land degradation types of 4 choosed areas(Chuxiong City in Yunnan Plateau(degraded area is 1159.44 km² and makes up 26.17% of the total area), Suining City in hilly area in middle Sichuan Basin(degraded area is 3188.51 km², makes up 59.93% of the total area), Bijie Prefecture in lime stone area in Guizhou Province(degraded area is 9055.30 km², makes up 33.70% of the total area) and Yuanmou County in dry-hot valley in Yunnan Province (degraded area below 1350m of altitude is 1006.02 km², makes up 70.15% of the total area)),discussed land degradation process(The land degradation process is under fragile eco-environment(great height difference, steep slope, frequent heavy rain and rainstorm),human unreasonable social-economic activity (reclaim slope land, cut forest, over grazing, etc.) caused the process of land degradation), proposed ways(prevention and control of land degradation by the law; strictly control population with the N range of the equation: 0.2113K <0.7887 K (K is the environment bearing capacity); strengthen agricultural basic construction and adjust agricultural structure; strengthen forest protection and afforestation; control livestock quantity and grazing intensity) to control and regulate land degradation.