Abstract: The Silk Road Economic Belt is a great national strategy for opening to the west and promoting economic cooperation with the surrounding region. Speeding up the transportation infrastructure construction is a principal measure to boost the construction of the Silk Road Economic Belt and promote the inter-state connectivity. Applying traffic network dimension, correlation coefficient and Granger causality test, we studied the dynamic change of transportation investment, track network development, traffic capacity and the impact on economic development of the Silk Road Economic Belt, 1998-2015. The results show that the transportation investment of 9 provinces in the Silk Road Economic Belt presented an increasing trend as a whole, and the speed of 4 southwest provinces was faster than that of the northwest provinces. The track network density was slower than the national average obviously, and the railway network density and the road network density in 2015 were respectively 0.04 km/sq.km and 0.14 km·km^-2 slower than the national average. Development degree of track network was not high. Traffic network dimension increased in 1998-2015, and the railway network dimension increased from 1.16 to 1.26, the road network dimension increased from 1.28 to 1.30, but always lower than the national average. This indicates that the traffic development degree of Silk Road Economic Belt was still lower than other regions. The track network development of the 4 southwest provinces was better than that of the 5 northwest provinces. The passenger and cargo capacity of the Silk Road Economic Belt showed an increase trend in 1998-2015 with the improvement of the Silk Road Economic Belt transportation conditions. The passenger and cargo capacity and turnover ability were gradually improving, and railway freight turnover capacity rose dramatically, but the status of road freight turnover throughout the country declined. Selecting gross domestic product(GDP)in 1998-2015 and fixed assets of traffic facilities construction( TI )as sample data, applying correlation coefficient analysis, this study demonstrates that transport infrastructure investment of the Silk Road Economic Belt had significant impact on the national economic development. The promotion of transportation infrastructure to the gross national product delayed for two years, and Gross national product had a direct effect on transport infrastructure investment in the same year. The spatial spillover effects of transportation infrastructure were not sizable, which indicated that the economic relation between different provinces was still weak. The innovation point of this essay is to reveal spatial-temporal evolution of the transportation network and its impact on economic development in Silk Road Economic Belt by qualitative and quantitative combined analysis, and this study could provide a scientific basis for promoting the economic development and the traffic infrastructure construction of the Silk Road Economic Belt.

Key words: Silk Road Economic Belt(SREB), track network development, traffic capacity, spatial-temporal evolution