Based on Prata parameterization of clear sky downward longwave radiation and in view of its poor theoretical accuracy in plateau areas and areas with small precipitable water vapor, three new parameterizations of clear sky downward longwave radiation are proposed in this paper, in which air pressure is considered because longwave radiation from different length of atmosphere column is different. Empirical constants are obtained by least square fitting of global ERA5 reanalysis data and their applicability is analyzed in different regions of the world. The simulation results show that parameterizations with consideration of air pressure can effectively improve the convergence of atmospheric emissivity of Prata scheme when the precipitable water vapor can be reduced. The mean bias errors and the root mean square errors of the simulation values of the downward longwave radiation of the new schemes in Amdo Area and San Luis from the observation values are obviously smaller than that of Prata’s 〖JP2〗parameterization scheme. Compared with Prata’s scheme, the simulation accuracies of the new schemes are improved and the applicabilities are better.