Two possible structures of Mo 8O 4- 26 were optimized using the Polak-Ribiere method of Molecular Mechanics Optimization and the termination condition is RMS (Root-mean-square) gradient of 0.42 kJ/mol. Based on the calculations of the molecular dynamics, Lengevin dynamics and Monte Carlo dynamics simulation, the structure models of Mo 8O 4- 26 with the lowest energy were acquired respectively according to the energy of the systems calculated using the ZIDO/1 and PM3 methods. The total energy, energies of some frontier molecular orbitals and atomic charges of Mo 8O 4- 26 were computed at the HF/3-21G and HF/STO-3G levels. The calculation results show that the contortion of the structure with eight MoO 6 is smaller than that of the structure with six MoO 6 and two MoO 4. The total energies of the two structures are nearly equal because the contortion of the structure with six MoO 6 and two MoO 4 would make the exclusion force decreased. Two possible structures of Mo 8O 4- 26 were optimized using the Polak-Ribiere method of Molecular Mechanics Optimization and the termination condition is RMS (Root-mean-square) gradient of 0.42 kJ / mol. Based on the calculations of the molecular dynamics, Lengevin dynamics and Monte Carlo dynamics simulation, the structure models of Mo 8O 4- 26 with the lowest energy were acquired respectively according to the energy of the systems calculated using the ZIDO / 1 and PM3 methods. The total energy, energies of some frontier molecular Orbitals and atomic charges of Mo 8O 4- 26 were computed at the HF / 3-21G and HF / STO-3G levels. The calculation results show that the contortion of the structure with eight MoO 6 is smaller than that of the structure with six MoO 6 and two MoO 4. The total energies of the two structures are nearly equal because the contortion of the structure with six MoO 6 and two MoO 4 would make the exclusion force decreased.