Abstract: In this paper a formula is derived for shear dispersion coefficients of two dimensional tidal flow, the velocity distributions of which can be expressed by the product of a space-dependent function and a time-dependent function, by the method of concen-trational moment. The process of dispersion coefficients versus time is calculated in case of sine tidal flow with logarithmic velocity distribution. The relation of dispersion and features of tidal flow, and the phenomenon of negative dispersion are analyzed...