Abstract: In this paper,by using the modal dispersion equation with the phase-integral approaches,and considering an eddy (or water mass) as a sound channel disturbance,the effects of the undisturbed channel,coldreore eddy and warm-core eddy on the acoustic propagation characteristics are discussed.According to the solutions of the dispersion equation,the relation is obtained between the modal phase velocity,group velocity and interference distance,and the eddy intensity.When the plane wave (with an incident angle α) travels toward the center of a warm-core eddy (intensity B_M),'double channel phenomenon'will take place in case of sin² α<B_M<2(l-cos α),and then the modal phase velocity and interference distance will have anomalous changes which are completely different from the case of the colducore eddy.