Abstract: In order to study the quantitative characterization of magnesite grinding degree, grinding test, particle size detection test and grinding fineness test were carried out with the raw material of magnesite derived from Dandong area of Liaoning Province. Based on the fractal theory, a mathematical model of volume fractal dimension was established to characterize the particle size distribution of magnesite grinding. The results showed that the volume fractal dimension has a non-linear relationship with the grinding fineness. When the mean value of volume fractal dimension reaches the maximum value, that is, D₃=2.4662, the corresponding grinding fineness of -0.074 mm is 81.6%, while the flotation test obtained the optimal flotation index. Quantitative characterization of magnesite grinding degree was realized, and the relationship between volume fractal dimension and flotation was established in this paper.