3-Methyl-4-(3-benzoxy-4-methoxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-one molecule was optimized by using the B3LYP/HF 631G(d,p) and B3LYP/HF 6311G(d,p) basis sets. This optimized structures used to calculation of the different theoretical properties of the compound. 1H-NMR and 13C-NMR isotropic shift values were calculated by the method of GIAO using the program package Gaussian G09W. Experimental and theoretical values were inserted into the graphic according to equitation of δ exp=a+b. δ calc. The standard error values were found via SigmaPlot program with regression coefficient of a and b constants. The veda4f program was used in defining IR data. IR absorption frequencies were compared with experimental data. Infrared spectrums were composed by using the data calculated. Additionally, bond lengths, dipole moments, HOMO-LUMO energys, mulliken charges by using the B3LYP/HF 631G(d,p) and B3LYP/HF 6311G(d,p) basis sets of this compound were theoretically calculated. Finally, theoretical properties of the compound according to two different basis sets were compared.