Abstract:A forecast method of extended range is introduced. By usi ng the global model of the grid prediction of 500hPa height fields in the Europe an Ce nter for Medium Range Weather Forecasts（ECMWF）, the correlations between the predicted value and NCEP reanalysis data of 500hPa height fields at the same time in the past years are obtained. Among these correlations，three l argest correlat〖JP2〗 ion coefficients are picked out. Meanwhile, by using daily observed precipitatio n d ata in the past years, daily probabilities of sunny, light rain, moderate rain, heavy rain and rainstorm are gained which are treated as background probabilitie s. The best related year is computed with control of the background probabilitie s. Taking observed precipitation in that year as the predicted one, so that the prediction for the extended range (10-20 days) will be made.Operational experimentation and verification show that the method is effe ctive.