Abstract: The conductivity of metallurgical grade silicon (MG-Si) in different purities and thicknesses was measured under different temperatures by self-designed test equipment. The influence of MG-Si purity on the conductivity was analyzed. The results show that the thinner silicon wafer can reflect the relationship between its conductivity and temperature accurately. When the temperature was above 650 ℃, the conductivity of MG-Si increased rapidly responding to the obvious effect of intrinsic excitation, and the conductivity of higher purity MG-Si containing fewer metallic impurities increased considerably with the increase of temperature. Finally, the mathematical expression of the conductivity of MG-Si with temperature changes was obtained by numerical fitting according to the measured conductivity values.