Abstract: Usually we use ITU-R P.617 recommendation to compute the troposcatter propagation loss of low scatter angle case, however, it is not fit for the high scatter angle case. We propose an improved method for high scatter angle case in this paper, and analyze the reason why it is not fit for the high scatter angle case. We find that the height of the common volume above the line of transmitter and receiver called H maybe smaller than the height above the ground called h, but from the physical meaning, H must be larger than h. So according to the geometry model, we replace the original expression of H, and in an approximate condition we suppose the two heights are equal. If we substitute the new expression into the link prediction, we find that it is improved well compared to the original results and closer to the experimental results. The proposed method is also agreed well with complex U.S.National Bureau of standards (NBS) method which is used for both low and high elevation.