Drilling cuttings, the primary byproduct generated from the exploration and mining of shale gas, are potentially hazardous types of waste that seriously deplete land resources and pose environmental safety problems. In this paper, oil-based drilling debris is used as a typical porous medium phase solid waste, and the law and characteristics of unsteady diffusion and release of PAHs are studied under the specific situation of oil-based drilling debris with different thicknesses as the "source". The results showed that(1) Thickness has a greater influence on the diffusion and release law of PAHs from oil-based drilling cuttings residues, the diffusion release of PAHs increases with the increase of sample thickness. (2) The thickness of the porous media source is the main influencing factor of the PAHs diffusion and release diffusion related parameters. The higher the thickness, the diffusion coefficient Dm increases with the increase in thickness. The distribution coefficient K and the initial diffusible release concentration Cm0 change in a similar manner, and both increase with the thickness.