Abstract: The characteristic equation for leaky Lamb waves in a three-layered structure with loading liquid is derived in this paper.A mathematical algorithm is developed for estimating the dispersion and attenuation of leaky Lamb waves in an aluminum/water/aluminum structure immersed in water.The propagation properties of leaky Lamb waves are analyzed and compared with the classical Lamb waves in the same layered structure without loading liquid.By tising a broad-band ultrasonic transmission spectrum measurement system,the dispersion of leaky Lamb waves is measured.The predicted and experimental results are found to be in good agreement.