In this study, 25 pairs of forest and farmland plots were selected in Yunnan Province to analyze and compare the topsoil (0-10 cm) magnetic characteristics and their relationship with environmental factors. The results showed that: 1) χ_lf ranged from 13.04×10^-8to 1 023.2×10^-8m³/kg for forest soils, and from 10.90×10^-8 to 828.94×10^-8m³/kg for cultivated soils, both showed great variations. The values of various magnetic parameters were irregular both in forest and farmland topsoils, and no significant difference between the average values of various magnetic parameters of forest and farmland topsoils. 2) Fine-grained (SP+SD) ferrimagnetic minerals were the main magnetic minerals in both the forest and farmland topsoils, while a small amount of antiferromagnetic minerals were found in some topsoils. The types of magnetic minerals were consistent in the same groups of the forest or farmland topsoils. 3) The magnetic properties of the forest and farmland topsoils were related to various environmental factors such as soil weathering degree, nutrient elements and water content. Different environmental factors had different contributions to soil magnetic changes under the two types of land uses, among of which, the weathering degree and organic carbon contributed the most to the magnetic properties of forest and farmland topsoils respectively.