Abstract: Meteorologists in Guangxi have been working on the analysing and forecasting of sustained cold temperatures and rains in spring. Mainly composed of statistic techniques, their forecasting means fail to meet the demanding service in terms of the period of forecast validity.At present, long term NWP in the world is the one that employs GCM as monthly mean circulation. In China, Zheng Qinglin's 7-layer global general circulation spectral model has been successfully used in long term NWP research. Based on his work, modifications are made in this paper so that the forecast error remains lower than that for persistence throughout the 30-day simulation. 30-day mean Eurasian 500 hPa circulation and day-to-day variations for day 1-10 are close to reality.