We sampled and tested the magnetic susceptibility of surface soil (0∼30cm) and profile soil of red bare lands in the karst area of eastern Yunnan,China. The results showed that the magnetic susceptibility of the surface soil in the 15 samples of red bare lands was lower than that of vegetated lands in the same area,which was 7∼67% lower, respectively. The mean value was 994.14×10−8m3⋅kg−1, which was 39.84% lower than that of the vegetated lands, and the variation coefficient was 36%, higher than that of the vegetated lands. The profile soil’s variation coefficients of the magnetic susceptibility in the red bare lands were 5.3% and 16.8% respectively, which were lower than those of the vegetated lands (31.5% and 25.3%). The conclusion is as follows: the soil of red bare lands is rich in magnetic minerals; the surface soil’s susceptibility is lower than those of the vegetated lands in the same region and the degree of variation is higher, while the degree of profile soil’s variation coefficients of the magnetic susceptibility is lower. We can conclude that there is a chemical erosion process which a large number of magnetic minerals are lost or transformed in the erosion process of red bare lands, and the acid rain may be one of its important causes.