Abstract: The variation law of annual maximum peak discharge time series at Cuntan station of the upper reaches of Yangtze River has been prabed，including trends and periods analysis．And the results have shown that there are no trends for annual maxium peak discharge and the major periods are 4a，9a，lla，29a．On the other hand，the long-term forecast of annual raaximlnl flood peak discharge has Men researched with the pard method combined with the stochastic method ．The forecasting result is good：the qualification rate in the calibration period is 84．61％ and in the verification period is 80％ ．So the model can be applied to long-term forecast．The research plays a great role in operating and managing the Three Gorge hydropewer station．

Key words: long-term forecast, annual maximum peak discharge, period, the upper leaches of Yangtze River

摘要： 从趋势分析和周期分析两方面分析长江上游寸滩站年最大洪峰流量演变规律．研究表明，寸滩站年最大洪峰流量序列未发生趋势性变化；其主要周期为4a，9a，1la，29a．在此基础上，应用周期与随机模型组合方法对寸滩站1939—2004年最大洪峰流量序列进行预报．率定期的合格率为84．61％，检验期合格率为80％，预测效果较好，该模型可以应用于长期预报中研究成果对长江三峡水库防洪调度有重要的参考价值．

关键词: 长期预报, 年最大洪峰, 周期, 长江上游