The mechanism of magnetic susceptibility (χ) of soil derived from basalt in Zhejiang and Yunnan Provinces was studied by applying mineral magnetic measurement technique and X-ray powder diffraction. Results showed that χ of soil derived from basalt in Zhejiang Province ranged from 100×10^-8-500×10^-8m³/kg. χ of soils derived from basalt in Yunnan Province ranged from 500×10^-8-2000×10^-8 m³/kg. χ of synthesized goethite and hematite were 31.9×10^-8m³/kg and 84.5×10^-8m³ /kg, respectively. χ of synthesized iron oxides increased as aluminum-substituted amount of iron oxide increased. The magnetic parameter and X-ray powder diffraction pattern of soils indicated that χ of soil derived from basalt in Yunnan Province mainly contributed to the superparamagnetic maghemite and magnetite, which is pedogenic origin. χ of soils derived basalt in Zhejiang Province came from the contributions of both primary magnetic grains and secondary magnetic minerals, and hematite.