Abstract: Impacted by the coupling action among various factors such as resources，natural environment，social environment，technical conditions and so on，the imbalance is existed in the socio-economic development across the regions in northwest China，especially in the regional differences of transportation development. Based on the Exploratory Spatial Data Analysis （ESDA），this paper takes 51 cities （districts） of northwest China as an example to analyze the spatial disparities of the highway network as well as its correlation during the of period 2004-2010. Firstly，this paper selects the absolute density of each district's highway network per year as the evaluate index，and calculates the global spatial autocorrelation coefficient （Moran’s I Index） and the local indicators of spatial association （LISA） based on the spatial weight matrix. The calculate result of Moran’s I shows that the density of highway network in northwest China has a significant and growing global spatial autocorrelation characteristic，regional disparities trend of highway network is more and more obvious. Besides，the LISA directly shows that the region belongs to the highway network density “high-high”assemble type and the regions of “low-low”assemble pattern，has both expanded in different degree during the period of 2004 -2010．The interlocking region contains southern Shaanxi，Guanzhong area，eastern Gansu and southern Ningxia，is distributed as the highway network density "high-high" assemble type，while the “low-low ”assemble type area are mostly located in the Hexi Corridor，Xinjiang，Qinghai. Thirdly，this paper takes the ratio of each district's highway network density to the national average density as a measure index in analysis of the highway network development level. The result manifests that the highway network level of“Xi’an-Lanzhou-Xining”is now higher than the national average level，the region's outward diffusion ability has enhanced and it has formed a traffic belt by a stimulating effect on the surrounding regional highway network development. It is also necessary to strengthen the construction of highway infrastructures in which the highway network density is at a lower level. Finally，the article combines qualitative analysis with spatial econometric model to investigate the driving mechanism of the highway distribution differences. The natural environment is the basic constraining conditions of highway traffic infrastructure construction and operation. The imbalance pattern of regional economy development and it's spatial spillover effect is the important driving force in formation of highway network distribution differences.

Key words: highway network, spatial distribution, exploratory spatial data analysis, driving mechanism, Northwest China