The invention discloses a preparing method for a double-whisker compound modified shrinkage-resisting aluminum nitride substrate and belongs to the technical field of electronic packaging material preparing. By means of the preparing method, kaolin and sodium sulfate are taken to be subjected to mixing grinding, screening and sintering, a hydrofluoric acid solution is used for soaking and filtering after washing drying, washing drying is conducted after a filtering cake is obtained, and modified whiskers are obtained; then magnesium chloride, sodium borate and a potassium chloride solution are used for mixing calcination, deionized water is used for soaking filtering after a sintered material is obtained, filter residues are mixed with the modified whiskers and are mixed with polyvinyl butyral and the like to prepare a modified blank; the obtained mixture is subjected to ball grinding and screening and then is subjected to mixing grinding and defoaming with AlN powder and yttrium oxide, then tape casing is conducted, and a tape casting base is obtained; and the tape casting base is subjected to glue discharging treatment, then sintering forming is conducted, and the double-whisker compound modified shrinkage-resisting aluminum nitride substrate is obtained. The aluminum nitride substrate has the beneficial effects of being large in density, resistant to shrinkage and small in warping degree; and meanwhile the substrate has good heat conductivity and is an ideal electronic packaging material.