Several widely used downward atmospheric longwave radiation parameterizations for both clear-sky and all-sky were tested against 10minutes measured data from four stations at different surfaces in Heihe River Basin, northwest China. It can be inferred from the result that the Idso clear-sky equation was in good agreement with the observed data in all stations, even without adjustment to the observations, while Dilley & Obrien equation had the best result after being adjusted. Both equations were more sensitive to air temperature than water vapor pressure. Maykut equation was found best in cloudy-sky, but the simulated radiations didn’t fit well with  measured flux.The diurnal and seasonal variations of downward longwave radiation were further studied. The predictions of Idso and Dilley & Obrien equations showed the diurnal characteristics of downward longwave radiation under clear-sky conditions. The worst estimation of the model was before sunset, which  was mainly caused by the temperature inversion phenomenon in the night. The longwave radiation had no obvious diurnal characteristic in the cloudy-sky days. For seasonal variations, both models had much better estimation in autumn-winter than spring-summer period, also the coefficients in each period were also  obtained.Based on the results of this study Idso and Dilley & Obrien equations were recommended for clear-sky days and Maykut model for all-sky when  longwave radiation is calculated  in a similar climate.