This paper is devoted to the study of the propagation of tide wave in a basin with variable cross-sectional area. With the W.K.B. method an analytic solution of amplitude is obtained. It is found that the motion of co-oscillating tide wave in a basin with variable cross-section is a progressive one, depending on the cross-section as well as the frictional force. The effects of friction on the motion of tide wave is discussed in detail. This paper is devoted to the study of the propagation of tide wave in a basin with variable cross-sectional area. With the WKB method an analytic solution of amplitude is obtained. It is found that the motion of co-oscillating tide wave in a basin. with variable cross-section is a progressive one, depending on the cross-section as well as the frictional force. The effects of friction on the motion of tide waves is discussed in detail.