Ultrasonic velocities of binary liquid mixtures of methyl benzoate with 1-octanol are measured using ultrasonic interferometer at 303.15K,308.15K,313.15K and 318.15K over the entire range of composition. Theoretical values of ultrasonic velocity have been evaluated at the four temperatures using Nomoto’s relation, Ideal mixture relation, Impedance relation, Rao’s specific velocity relation and Junjie’s method. Theoretical values are compared with the experimental values and U2 exp/U2 imx is evaluated for non-ideality in the mixtures. A good agreement has been found between experimental and theoretical values of ultrasonic velocity. The relative applicability of these theories to the present systems has been checked and discussed. The results are explained in terms of molecular interactions occurring in these binary liquid mixtures.