Air freight market is one of the most important parts in the global air transport market, which is closely linked to global economy and trade. The development trends and demands of air freight market will directly affect freighter fleet development tendency and planning. As the carrier of air freight market, freighters, especially long range widebody freighters make a significant contributing to the international transporting and communicating. The mainstream forecast method is based on correspondence between demand and supply. The forecast process is very complex and the accuracy is very high. The disadvantage is the long forecast period and the results cannot be gained rapidly. This thesis models a GM（grey model） (1, 1) of wide body air freighter forecast based on the grey forecast method. The model can forecast the future wide body air freighter fleet development, which can meet normal forecast precision requirement quickly and efficiently.