An efficient synthesis of 3-methyl-4-(arylmethylene)isoxazol-5(4H)-ones are developed via cyclocondensation in 84-94 % yields starting from aromatic aldehydes, hydroxylamine with ethyl acetoacetate vitamin B 1 is catalyzed under ultrasound radiation, and are characterized by HR-MS, FT-IR and 1 H and 13 C NMR spectroscopy. The reaction has simple operation, metal-free catalysis, acid or base free catalysis. As a green catalyst, vitamin B 1 is found to possess favorable catalytic activity and reusability for the condensation reaction. 5-(2-Hydroxy-3-methoxybenzylidene)-3-methylisoxazol-5(4H)-one as a metal ion fluorescent probe, has excellent selectivity to Sr 2 + and exhibits obvious discoloration. Fe 2 + quenches the fluorescence of the ligand 3-methyl-4-(2,3,4trihydroxybenzylidene)isoxazol-5(4H)-one, and exhibits an obvious color change.