Acoustic impedance of aging epoxy coating in nuclear plant is measured for evaluation of the degradation of the epoxy coating using a new ultrasonic measurement technique that uses a specially designed conical acoustic lens to determine the reflection coefficient (reflectance) of the epoxy coating. Reflection waves measured at two different vertical positions slightly apart from each other are subtracted and used to calculate the acoustic impedance of the epoxy coating. Epoxy coated concrete specimens are fabricated and degraded artificially under accelerated aging conditions to determine the acoustic impedance of the films. Experimental results show that the acoustic impedance is very sensitive to the degradation of coating and can be applied to evaluate the quality of the epoxy coating quantitatively.