The synthesis of 3-aminofurazan-4-carboxylic acid was improved, and it was synthesized via substitution, annulation-salt forming reaction and hydrolysis, using cyanoacetate as raw materials. The structure of the product is charactered by IR, NMR and MS. The effects of substrates ratio, reaction temperature, reaction time and solvent on the annulation-salt forming reaction was investigated. And the reaction time and solvent and pH on the hydrolysis was also investigated. It is suggested that the increase of KOH, the increase of reaction temperature can improve the yield of the product. The best annulation-salt forming reaction condition is the mole ratio of hydroxylamine hydrochloride : KOH : methyl-2-cyano-2-(hydroxyimino)acetate =1:4:1, the condensation temperature is 25℃, the reaction time is 2h, the cyclization temperature is 80℃, the reaction time is 2h, the solvent water is 50mL. The best acidification reaction condition is the reaction temperature is 5℃, the solvent water is 30mL, pH＜1. The total yield of annulation-salt forming reaction and hydrolysis was 79.7%, which is higher than the yield of 64% in the reported article.