Vegetable greenhouses, as semi-enclosed systems, exhibit unique mercury (Hg) dynamics due to elevated temperatures, which enhance Hg(0) volatilization from the soil, leading to atmospheric Hg(0) accumulation. This poses the dual risks of direct crop contamination and secondary pollution through foliar uptake. This study investigates the effects of air purification combined with UV light on atmospheric Hg (GEM) concentration and soil Hg(0) emission flux in a simulated vegetable greenhouse, as well as the underlying mechanisms of Hg migration and transformation. The experimental results show that air purification significantly reduced the GEM concentration in the greenhouse, with a decline rate of over 79% (from 9164.12 ng m-3 to 1892.61 ng m-3) within 10 hours. Additionally, it inhibited soil Hg(0) release, with a reduction of over 72% (from 24087.98 ng m-2 h-1 to 6570.96 ng m-2 h-1) in the Hg(0) emission flux. Hydroxyl radicals (·OH) generated by UV photocatalysis promoted Hg(0) oxidation and absorption reactions, significantly enhancing the conversion efficiency of Hg from the gas phase to the liquid phase. Fluid dynamics simulations revealed that air circulation accelerated the optimization of Hg migration pathways and slowed the accumulation of local Hg concentrations. Mass balance analysis indicated that Hg in the greenhouse forms a dynamic equilibrium between soil, gas, and liquid phases, with air purification effectively regulating this process. This study provides scientific evidence and technical support for Hg pollution control in agricultural environments and offers a reference for optimizing greenhouse management and achieving sustainable agricultural development.