The method for analysis of spatially – temporal distortions of a pulsed light beam in the stratified turbid medium with narrow scattering phase function (in particular, sea water) is developed. It is shown that the radiative transfer equation in the refined small-angle approximation is reduced to a set of equations for longitudinal moments of a pulsed light field which is solved rigorously unlike the analogous equations for temporary moments of pulse. Recurrence relations, which permit to calculate the moments of the higher order based on the zero moment, are obtained. The formulas for calculating the first three moments, defining the average radiance (or irradiance), the distance between the leading front and the “centre of gravity” of pulse as well as the longitudinal scale of its smearing, are given. Formulas for definition of time characteristics of pulse from its spatial moments are obtained.