Parabolic equation is an efficient model to simulate the characteristic of wave propagation. The atmospheric absorption is ignored by parabolic equation model in present; however, the atmospheric attenuation is an important limiting factor of terahertz(THz) communication. Based on the complex refractive index in atmosphere, the parabolic equation model for estimating atmospheric attenuation of THz wave is proposed. The model takes into account the effects of meteorological parameters variation with height and calculates the atmospheric attenuation in different seasons and regions, which matches with the actual environment. Finally, the model is applied to simulate the transmission characteristic of 0.14 THz wave. The propagation losses versus range and height are presented and compared with the results of ignoring atmospheric attenuation.