Abstract: The demands for ultra long-distance troposcatter communication is greatly increased. However, according to actual measurement, current methods of transmission loss prediction is not suit for ultra long-distance links. In this paper, a correction method of the transmission loss prediction for ultra long-distance troposcatter links is mainly discussed. The proposed method is developed based on ITU-R P.617-3. Through practical experiments and measurements, it is proved that the proposed method is effective and accurate. This correction method could provide reliable reference for the design of ultra long-distance troposcatter communication systems.