Because the weather conditions in different sea areas are different, the evaporation duct occurring over a large sea surface is normally regional and range-dependent. This property results in the fact that the radio wave propagation within the environment of this type is distinct from that within the range-independent evaporation duct environment. Therefore, it is meaningful to perform the regional range-dependent evaporation duct inversion for accurately predicting radio wave propagation and improving radar performance. From among the variety of ways of detecting evaporation duct in practical application, we adopt the regional modified refractivity profile of evaporation duct predicted by the mesoscale numerical weather model MM5 as the prior information, and propose a posterior probability estimation model of the regional range-dependent evaporation duct on the basis of the radar sea clutter power. First, in this model we use the principal component analysis method to model the range-dependent property of evaporation duct, and on this basis, establish the inversion procedure of the range-dependent evaporation duct by using the radar sea clutter. Then, we obtain the relationship among prior probability distribution, posterior probability distribution, and likelihood function of the parameters of the modified refractivity profile by using the Bayesian theory, and finally realize the maximum posterior probability estimation of the evaporation duct parameters. By estimating the real regional range-dependent evaporation duct over East China Sea, it is indicated that the proposed model can perform the inversion of regional range-dependent evaporation duct with a higher precision.