A four-step reaction synthesized 5-(4-nitro-1,2,5-oxadiazol-3-yl)-5H-［1,2,3］triazolo［4,5-c］［1,2,5］ oxadiazolium inner salt(NOTO). The first step is the oxidation of diaminofurzan (DAF) with Caro′s acid giving 3,3′-diamino-4,4′-azoxyfurazan(DAAzF) in yield 88.8%. The second one is the reduction of DAAzF by Zn dust(this technology was firstly applied) to 3,3′-diamino-4,4′-azofurazan(DAAF), the key intermediate, in yield 92.2%. The third one is the cyclization of DAAF in the presence of diacetoxyl iodobenzene giving 5-(4-nitro-1,2,5-oxadiazol-3-yl)-5H-［1,2,3］triazolo［4,5-c］［1,2,5］ oxadiazole (AMOTO) in yield 87.7%. The last one is the oxidation of AMOTO with Caro′s acid resulting in NOTO in yield 25.0%. The total yield of NOTO (based on DAF) is 17.5%. The optimization of reaction conditions and the improvement of the post-treatment for the cyclization made the yield and purity of AMOTO up to 87.7% and 99.4% respectively. The structures of all intermediates and the product were confirmed by a number of analytical techniques. In addition, the cyclization mechanism was proposed and