Fractal theory could provide quantitative basis for such aspects of the basin as its complex landform and its development process. For further study of river fractal dimension, the authors extracted the river networks of Golmud River basin on the basis of the ASTER - GDEM data and according to different confluence accumulation thresholds. Using the hydrologic analysis model of geographic information system, the authors calculated the corresponding river fractal dimension with the box dimension method so as to describe the topography characteristics of the valley and predict the evolution trend of drainage landform. The results show that, in some non - standard ranges, concentration accumulation thresholds fit fractal dimensions well. The fractal dimension values of Golmud River basin are approximately between 1. 6 and 1.8, suggesting that this basin is in the mature stage of geomorphological erosion and tends to develop into the late mature stage. The terrain rises and falls greatly with the fragmentation of the ground. The erosion of rivers is mainly lateral,and the down -cutting is relatively weak. This conclusion is in consistency with the calculation result of the hypsometric integral.%分形理论为流域的复杂地貌形态及其发育过程等方面提供了定量依据,为进一步深化流域水系的分形研究,以ASTER-GDEM数据为基础资料,运用GIS水文分析工具提取了格尔木河流域在不同汇流累积量阈值下的水系河网；并用盒维数法计算了相应的水系分维数,以此来描述流域的地貌形态特征；并进一步预测流域地貌的发育演化趋势.研究结果表明:在一定无标区间范围内,汇流累积量阈值和分维数拟合较好；计算得到格尔木河流域的水系分维值处于1.6～1.8之间,据此可以判断出该流域处于地貌侵蚀发育壮年期,并向壮年晚期发展,流域地势起伏大,地面切割得支离破碎、崎岖不平,河流以侧蚀为主,下切作用相对较弱,与流域高程面积积分值计算所得结论一致.
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