The kinetics of absorption, desorption, and degradation of sulfur mustard (HD) in alkyd coating was experimentally studied, and a one-dimension mass transfer model for the transportation of HD molecule in alkyd coating was established on the experimental data. The obtained results indicated that the persistence of HD molecule could be greatly increased due to the absorption of HD droplets by alkyd coating, and there still occurred the desorption of HD as vapor from coating for more than 3 days even after decontamination of HD droplets onto coating. It was also experimentally shown that the majority of HD both absorbed and desorbed was accomplished at an early stage, less than 10 h, and HD molecule was able to be degraded within the alkyd coating probably through the reactions of hydrolysis and elimination. The diffusion coefficient and degradation rate constant of HD in alkyd coating were determined to be practically around 10(-9) cm(2)/s and 2.4 x 10(-5) min(-1), respectively.