Abstract: α-alumina nanopowder was prepared by sol-gel method with industrial pure alumina sol as raw material,zinc fluoride and ammonium nitrate as mineralizers respectively.Thermogravimetry-differential scanning calorimetry (TG-DSC),field emission scanning electron microscope（FE-SEM）,X-ray diffraction (XRD),and Zetasizer were used to characterize the thermo-reaction properties of samples.Results showed that the phase transformation temperature of θ-alumina to  α-alumina can be reduced by about 100 ℃ under the same condition,and the gained α-alumina nanopowder possesses smaller grain size and narrower grain size distribution by adding ammonium nitrate compared with zinc fluoride.Different mineralizers have different effects according to the different reaction mechanism of mineralizers.Then,reaction mechanism of mineralizers was analyzed and researched.