The density-functional theory(DFT) method of the Amsterdam density functional (ADF) was used to calculate the geometry and frequency of 4-amino-1,2,4-triazol-5-one (ATO). The calculated results were compared through varying basis sets and relativity effect. The geometry, Mayer bond orders, net charges of atoms, frontier orbital energy and the main atomic orbital percentage were calculated. Results indicate that the basis sets in ADF program have a great influence on the calculation. Results obtained by the basis set of TZP are good conformity with the experimental. The crystal field theory was used to calculate the energy band structure and density of state (DOS) on ATO. The properties of ATO are similar to insulators.