A sensor which measures physical parameters of a liquid with high sensitivity and accuracy is in great demand in medicine, biology, chemistry and environmental science [1]. Recently, resurgent interest in Lamb waves was initiated in their applications of multisensors [2]. The principle of these Lamb-Wave Sensors is that the propagation velocity of Lamb waves changes when a plate is bordered with a liquid. In this paper, we report the results of our recent theoretical investigations of the effects of bordering liquid layers on the propagation of Lamb waves in a solid plate.