Abstract: This paper consists of two parts. First, an analysis has been made on the errors in geopotential height at 500 hPa in 48 hours in Eastern Asia in summer 1982 by the operational numerical model given by SMA. It is found that the errors in the middle and high latitudes (to the north of 40oN) are much smaller than that in the subtropical and tropical regions. Second, we have made the expansion of the geopotential height at 500 hPa in middle and subtropical latitudes respectively, and have found that there is a definite relation between them. According to this relation, a statistical method for the 48-hr prediction of the geopotential height at 500 hPa in Eastern Asia in summer has been developed. We found that the 48-hr prediction of the height field in the subtropical region, especially the intensity of the subtropical anticyclone in the Northwest Pacific, is much better than the prediction given by the operational numerical model.