Abstarct: We have described one-pot solvent-free efficient method for the synthesis of 2H-indazolo[1,2-b]phthalazine-triones derivatives via the nanoboehmite suhfamic acid catalyzed reaction of diketone, aldehyde and phthalhydrazide at 100°C. The simplicity of the system, the good yields, the shorter reaction time, an easy of work-up make the described method for the synthesis of 2H-indazolo[1,2-b]phthalazine-triones an attractive manner, which can be extended to the synthesis of the other heterocyclic compounds.