Abstract: This paper presents an exact solution based on the wavenumber-integration theory for the acoustic field in a shallow-water environment consisting of a homogeneous layer below the sea-surface,a thermocline,a homogeneous layer above the bottom,and a liquid,homogeneous seabed.Detailed derivations are given,where both of the pointand line-source cases are considered.Besides,the presented method is also applied to the study of underwater pulse propagation.Waveforms of received signals are calculated with the presented method,with the environmental data measured during an experiment.The calculated time interval between two adjacent pulses is in excellent agreement with the estimated value by the ray theory.The presented method is well suited for scenarios where the acoustic field is required to be computed a huge number of times,for instance,in simulations of the pulse propagation problem,the geoacoustic inversion problem,etc.