Objective To study the effect of magnetization on surface tension of herbicide solution and particle size of herbicide spray droplet, and explore a new control method of particle size of herbicide spray droplet.Method The surface tension experiment of the magnetized herbicide solution and the particle size experiment of the magnetized spray droplet were designed to record the surface tension value of the herbicide solution and the particle size value of the spray droplet under the influence of two factors of different magnetic field intensity and magnetization duration, observe the change rule of the data, and fit the data, and give the functional relationship that conforms to the description of the data change.Result When the magnetic field intensity was 50−500 mT and magnetization duration was 5.0−25.0 min, both the surface tension of solution and the particle size of spray droplet decreased firstly and then rose with the increase of magnetic field intensity and magnetization duration. When the magnetic field intensity was 350 mT and magnetization duration was 15.0 min, the surface tension and particle size of spray droplet decreased the most. The surface tension value decreased to 54.0 mN/m with a drop rate of 14.96%, and the spray droplet size decreased to 108.75 μm with a drop rate of 11.20%. For surface tension data, the determination coefficient (R²) of Lorentz fitting function was 0.816 4, adjusted R² was 0.794 0, root mean square error (RMSE) was 1.105 9; And the R² of polynomial fitting function for spray droplet size data was 0.833 6, adjusted R² was 0.787 4, RMSE was 2.085 7. The fitting function was meaningful and the fitting precision was high. Conclusion It is not that the magnetization effect will be better with the increase of magnetic field intensity or magnetization duration, but that the optimal magnetization intensity and duration exist. The Lorentz model function given in this paper can be used as the function relation between the surface tension of herbicide solution and magnetization, and the cubic polynomial function can be used as the model for controlling the particle size of fog droplets under the magnetic field intensity of 350 mT.