The adsorption and desorption behavior of magnesium in soil is closely related to the balanced development of ecology and crops, and is of great significance for maintaining the normal ecological effects of soil. Phosphogypsum as a soil conditioner can change the physical and chemical properties of soil, and thus affect the adsorption and desorption behavior of magnesium in soil. In this paper, phosphogypsum and loess soil were used as raw materials to study the effect of phosphogypsum content on magnesium adsorption and desorption characteristics of loess soil. The results show that phosphogypsum have no effect on the adsorption of magnesium in loess soil, and proper amount of phosphogypsum can promote the adsorption of magnesium in loess soil, while the effect of incubation time on the adsorption of magnesium in loess soil is not significant. The magnesium isotherm adsorption process of raw soil and mixed soil samples conforms to Langmuir isothermal adsorption equation, and phosphogypsum hardly affects its adsorption thermodynamic characteristics of magnesium. The magnesium adsorption kinetics of the original soil and mixed soil samples meets the pseudo-second-order kinetics equation, and phosphogypsum do not change the adsorption kinetics of magnesium in loess soil. An appropriate amount of phosphogypsum can promote the desorption of magnesium in loess soil, but the effect of too much phosphogypsum on the desorption of magnesium in loess soil will be weakened, and may even inhibit the desorption of magnesium in loess soil.