A model for slopes of equilibrium range of wind-wave spectrum is first proposed on the basis of linear theory. The slope given by the linear model varies continuously from deep to shallow water, approximating to -5 in deep water and -3 in shallow water. In view of a considerable discrepancy between the theoretical results and experimental data, another model is then proposed on the basis of nonlinear consideration. The slope given by the nonlinear model is more consistent with the data measured in the field and laboratory, especially for shallow water, though the derivation of the model resorts to some assumptions and empirical facts. A model for slopes of equilibrium range of wind-wave spectrum is first proposed on the basis of linear theory. The slope given by the linear model varies continuously from deep to shallow water, approximating to -5 in deep water and -3 in shallow water In view of a considerable discrepancy between the theoretical results and experimental data, another model is then proposed on the basis of nonlinear considerations. The slope given by the nonlinear model is more consistent with the data measured in the field and laboratory, especially for shallow water, though the derivation of the model resorts to some assumptions and empirical facts.