Based on the ArcGIS spatial analysis function, the accessibility and correlation degree of urban public transport in Xining city are discussed by using the reachability model and the optimal scale decomposition method. The results show that the design of the bus line in Xining city is unreasonable, the line mileage and the non-linear coefficient of the line are out of the national standard, and the average level of the line network density is different. The accessibility is distributed from the center of the belt to the symmetrical descending distribution.The distribution degree and the distribution uniformity are low, and there are the regional superiority and the regional bad value. The spatial accessibility distribution is similar to the time accessibility distribution. The cost of accessibility is obviously different from the time and space accessibility.Comprehensive accessibility of the overall distribution presents the decreasing rule from the center to the surrounding, and correlating with time and space accessibility, and low correlating with the cost of relevance.To promote the public transport accessibility, it should improve the construction of hub station, increase the urban new district line, and promote the optimization speed of line network.

urban public transport； accessibility； spatial characteristics； Xining city