Abstract: A Scheme of simple radiative parameterization of ice clouds suitable for use in GCM model is presented. The importance of mixed-phase clouds in GCM climate simulations is investigated using this scheme together with UGAMP general circulation model. It is found that the change in cloud phase state and the effect of its feedback have a significant impact on the model climate. In the high latitude regions, the net radiation in the earth-atmosphere system could be increased due to the changes in cloud phase state, whereas the net radiation could be deceased in the tropics.