We made a detailed，empirical analysis of the railway network of China (RNC)，in which the stations are treated as nodes and a link exists between every two nodes if there is a train stop at each node. Firstly，we explore the statistical properties of the directed and weighted RNC with respect to the distribution of degree and strength，clustering coefficient and the shorted path length. The results exhibit that the distribution of degree and strength are between the exponential distribution and scale-free. Moreover，the RNC is a hierarchical small-world network. Secondly，the construction of the railway is the result of balance between the economical cost and the degree of need such as the population density and the number of administrative divisions. So the topological properties constrained by the geographic factors are taken into consideration，such as the relation between railroad length and degree，the density distribution of the stations and the population and the community strength of the province. These results proved that the RNC is constrained by the geography and approaches to the optimal construction.