Abstract: The low-grade diatomite of Linjiang，in Jilin Province is grade-three diatomite with high burning loss.The diatom of low-grade diatomite that mainly composed of coscinodiscus and a small amount of melosira，and gangue minerals are mainly quartz and albite.In order to improve the grade of diatomite and solve the existing problems such as long production cycle，high energy consumption and high water consumption，high consumption of acid，environmental pollution.For the first time，the reverse flotation behavior of low-grade diatomite was studied.The results indicated that under the conditions of flotation for purification pH 8，temperature of pulp of 40 ℃，sodium pyrophosphate dose as dispersion solvent，lurylamine dose as collector，and through the floatation process of one roughing and two cleaning，diatomite concentrate with the grade of SiO₂ 79.39%，the grade of Al₂O₃ 4.92%，the recovery rate of SiO₂ 5.00% was obtained，which reaches the standard of the secondary diatomite.Not only did the results confirm that the effectiveness of the reverse flotation for low-grade diatomite purification，also this method has many advantages，such as short production cycle，low energy consumption，low consumption of acid，low water consumption，and less environmental contaminating.

Key words: Low grade diatomite, Purification by reverse flotation, Laurylamine