Abstract: In order to study the effects of water droplet on the Lamb wave propagation, based on the principal of Lamb wave far-field scattering that generated from the interaction of Lamb wave and discontinuity of medium, an experimental monitoring on the far-field scattering signals of a sessile water droplet was implemented in this paper by using the sparse transducer array. Then the method of broadband chirp excitation and filtering extraction algorithm of narrow bandwidth response were studied, and an optimum selection of Lamb wave mode sensitive to surface water droplet and the center frequency as well the number of cycles was made. Finally a sessile water droplet of different volumes with the ellipse algorithm was located and imaged. The results indicate that the presence of a sessile water droplet has a significant influence on the propagation of Lamb wave A₀ mode where even small amounts of single water droplet can obviously affect the monitoring signals. The ellipse algorithm can locate and image a sessile water droplet, and the imaging color bandwidth is closely related to the imaging quality besides the size of water droplets.