The invention relates to a method for preparing a porous material surface layer gradient transition layer and belongs to the field of inorganic high temperature heat protection materials. The method comprises first coating the surface of a porous material with a solvent, forming a liquid phase guiding layer on a surface layer of a porous material, performing coating of solid liquid slurry, so thatthe coated solid liquid slurry permeates to an expected surface layer depth of the porous material under flow guide by a liquid phase solvent, the migration of a solid phase component in the solid liquid slurry towards a large depth pore can be effectively achieved, the formation of a filter cake is effectively avoided, so that the depth of the gradient transition layer is controllable, and a phase component is controllable; through a method of controlling a solid phase penetration depth through multi-time flow guide permeation, filling layer structures with different solid phase filling rates can be formed at different depth ranges, the transition layer capable of effectively relieving thermal stress can be formed, the surface layer strength of the porous material is greatly enhanced, and conditions are provided for follow-up preparation of a dense protective layer by the porous material.