The invention discloses a neuraminidase inhibitor and a preparation method thereof. The preparation method comprises the following specific steps: (1) reacting diethyl oxalate with hydrazine hydrate to obtain monoethyl oxalate hydrazine; (2) reacting the monoethyl oxalate hydrazine with a benzaldehyde derivative in a solvent to obtain a monoethyl oxalate-[(aryl) methane] hydrazide compound; and (3) carrying out heating reaction on the monoethyl oxalate-[(aryl) methane] hydrazide compound and 4-morpholine propylamine in an organic solvent under the effect of a catalyst to obtain an acetic acid-2-[[3-(4-morpholine) amino]-2-oxo-2-[(aryl) methane] hydrazine neuraminidase inhibitor. The synthesized compound is novel in structure, and has good neuraminidase inhibiting activity.