Five soils derived from different parent materials were sampled from red so ll region of so uthern China and studied by magnetic methodology to understand to what extent iron reduction would afect so ll magnetic properties and how iron reduction would afect the magnetic minerals in soils. Reduction associated with organic matter decomposition strongly afected so il magnetic parameters at low pH. The losses of orlginal soil magnetic signals in terms of magnetic susceptibility (x), ‘Soft’isothermal remanent magnetization ('Soft' IRM), anhysteretic remanent magnetization (ARM)and saturation isothermal remanent magnetization (SIRM)at pH 4—6 during the two-month saturation treatment, were 66％～94％, 54％～90％, 64％～95％and 33％～83％, respectively. These changes were interpreted as a consequence of substantial dissolution of maghaemite and haematite in the soils. At pH 10, however, there was no significant magnetic changeobserved. M oreover, stable single domain soil maghaemite grains were also sensitive to red uction, which suggested that both pedogenic and detrital maghaemite were not stable in acid and reducing environments. Goethite, instead, was the most stable iron form under reducing conditions.