中文摘要：

在RS和GIS技术支撑下，利用城市空间紧凑度模型，分析西宁1987，1996，2001，2006年近20年的城市影像图。认为西宁城市空间形态呈现出“X”形，在城市空间形态演化过程中表现出扩张速度加快，湟水南岸扩张速度快于湟水北岸，并且主导西宁城市空间形态演化类型；从城市内部来看，近20年湟水北岸城市空间扩张以填充紧凑型模式演化，湟水南岸表现出从填充紧凑型过渡为外延扩张型为主。最后分析得出西宁城市形态跨河发展演化机制中，湟水、南川河与北川河流向奠定了其城市空间形态总体格局，交通网络体系起到了重要的引导作用，经济基础发挥了关键性作用等。

英文摘要：

With the RS and GIS technical support, using the urban＇ s space-compact model, the paper analyses Xining City＇ s images of 1987, 1996, 2001 and 2006 years. The conclusion is that Xining City＇ s spatial form showing ＂X＂ shape, in the course of evolution showing the rate of expansion accelerated, and also founds that the expansion rate of Huangshui southern coast bigger than that of Huangshui north coast, leads the type of Xining evolution of spatial form; Internally, in the latest 20 years, Huangshui north coast expansion type is filled compact, however, the south is transformed from mainly packed-compact to extension expansion . At last the paper analyses the evolution mechanism of Xining in the river-crossing, finding that the Huangshui, South river and North river＇ s flowing is the base to the overall pattern of Xining City＇ s spatial form, transport network system＇ s guiding role and economic base being the key role and so on.