Abstract: A theoretical model of ambient sea noise including surface sources and stratified ocean is discussed.The noise sources are assumed to be statistically independent directional acoustic sources situated on the surface,and the effects of ocean environment on ambient noise are studied.The normal-mode theory of surface-generated noise is developed,and the normal-mode formula of the directional density function suitable for small grazing angles is analytically continued to he consistent with the ray formula suitable for great grazing angles.The unified formulae to calculate the intensities,spatial correlation and vertical directivity of ambient noise are presented.