A simple and efficient synthesis of β-ketophosphonates was described. The hydrolysis reactions of alkynylphosphonates in the presence of sulphuric acid (3.5 mmol) as a catalyst in the recyclable ionic liquid N·(HSO4)2 afforded the desired β-ketophosphonates in excellent yields（98%）. This method has the advantages of metal-free and tolerance of multifunctional groups. Synthesized compound 2p has not been reported.