Abstract: In order to explore the migration and transformation law of benzene series (BTEX) under the fluctuation of atmospheric pressure, and improve the control level of soil and groundwater pollution in petrochemical-polluted sites, a refinery site in northwest China was taken as the research object and, combined with indoor soil column experiment and TMVOC software simulation, BTEX leakage simulation was carried out to explore the migration and transformation law of benzene in the vadose zone and aquifer under different amplitude of atmospheric pressure fluctuation. The results show that the atmospheric pressure cycle fluctuation can cause the gaseous benzene in the vadose zone to migrate to the non-equilibrium state, resulting in the increase of the gaseous mass fraction by 0.1%-0.5%. The conversion of non-aqueous liquid (NAPL) phase pollutants into vapor phase pollutants and their volatilization through the atmosphere is the main way of leakage quality loss, and this transformation will cause atmospheric pollution in the site and its surroundings. At the same time, the amplitude of atmospheric pressure fluctuation is negatively correlated with the time of gaseous transition. The study shows that the atmospheric pressure fluctuation significantly affects the phase transformation and migration process of benzene, promotes the phase transformation of benzene, and makes more benzene transform into gas, resulting in atmospheric environmental pollution.