Abstract: In order to improve the inversion precision of evaporation duct based on GPS signal and simplify the current refractive index profile model, we improve and put forward a new evaporation duct refractive index profile model-three parameter model on the basis of analysis of four parameter evaporation duct profile model sea surface scattering signal power characteristics.Then we compare the scattering signal power characteristics of each model by simulating and confirm that the new model have better sensitivity in application of inversion by particle swarms optimization algorithm.