The invention discloses a production method of flumioxazin. The production method comprises the following steps: by using 2,4-difluoronitrobenzene as an initial raw material, sequentially carrying out nitrification to obtain 1,5-difluoro-2,4-dinitrobenzene, and carrying out etherification reaction on the 1,5-difluoro-2,4-dinitrobenzene and butyl hydroxyacetate to obtain butyl 3-fluoro-4,6-dinitrophenoxyacetate; carrying out reduction cyclization with hydrogen to obtain 7-fluoro-6-amino-2H-1,4-benzoxazinyl-3(4H)-one; under alkaline conditions, carrying out alkynylation reaction with propargyl chloride to obtain an intermediate product; and finally, carrying out amidation reaction with 3,4,5,6-tetrahydrophthalic anhydride to obtain the flumioxazin. The production technique of the method has the advantages of short process, mild reaction conditions and cheap and accessible raw materials, and is convenient to operate; and the solvent used in the preparation process is recyclable. The method also has the advantages of high total reaction yield, high product purity, low production cost and low environmental pollution.