3,4-Bis(3′,5′-dinitrobenzene-1′-yl)furoxan was synthesized via five-step reactions of oximation,diazotization,denitrification,cyclization and nitration using benzonitrile as starting materials. The reaction conditions were optimized,and the cyclization could be performed at 2～10 ℃ within 3 h and Na₂CO₃ in excess of 20% with a yield of about 64.7%. The product′s structure was characterized by IR,NMR,MS and elemental analysis. In addition,the mechanism of the key reaction-cyclization was suggested. The vicarious nucleophilic substitution of hydrogen(VNS) reaction of the target compound was explored,and it could not go under the conditions applied by the authors. Furthermore,the thermal decomposition of this furoxan was studied with differential scanning calorimetry(DSC),IR,and thermogravimetry/mass spectrum(TG/MS),and the related mechanism was proposed and analysed in detail. The initial step of decomposition is dissociation of N—O bond with coordination oxygen in furoxan ring.