Poly-furazans on a chain(C_2nN_2n+2O_2n+3)(n=2-7) and on a circle (C_2nN_2nO_2n)(n=2-4，6) were optimized at B3LYP/6-31G theory level. The steady geometric configurations were obtained. The densities were calculated theoretically by Monte-Carlo method, and the enthalpies of formation were obtained by designing reactions having equal bonds and equal electronic pairs. The detonation velocities, detonation pressures and detonation heats were predicted by the formula of Kamlet. The relationships between detonation performance and n of two systems were studied, respectively. The results show that: (1) Detonation velocities, detonation pressures and detonation heats of two systems decrease with increasing of n; (2) The stabilities of poly furazans with oxy bridges on a circle are better than that on a chain when n is equal. Therefore,4，4′-dinitrobifurazan ether（n=2，chain）and 1，4-dioxino［2，3；5，6］oxadiazole（n=2，circle） are the target compounds for synthesis due to their good detonation performances.