1-(2-Hydroxyphenyl)-2-nitroethanone were synthesized through ring opening reaction of 4-Hydroxy-3-nitrocoumarin and the subsequent decarboxylation. Treating it with methoxyamine hydrochloride gave 1-(2-hydroxyphenyl)-2-nitroethanone O-methyl oxime, which underwent closing reaction mediated by sodium carbonate and gave 3-(methylimino)benzofuran-2(3H)-one oxime. Structures of all intermediates and target product were characterized by 1H NMR. The total yield was 70.4% and purity was as high as 99.2%. The synthetic process has features in high yield, easy operation, which are very promising in industrialization.