A novel and efficient method for the synthesis of N,N-dialkylamino/O-alkyl phenyl-2-(1-alkyl/phenyl-2-oxopropylidene) phosphonohydrazido oximes 4 using activated silica has been developed. The reaction involves the condensation of substituted alpha-ketooxime and N,N-dialkylaminophenylphosphonohydrazides or O-alkylphenylphosphonohydrazides and gave the corresponding phosphonohydrazido oximes in excellent yields under mild conditions.