Abstract Research purposes : The spatial dataset and Geographic Information System ( GIS) has already been utilized in many different engineering and research fields, such as National Land Resources Monitor, Water Resources Management,Transportation System Plan and Municipal System Plan,and so on. Because the spatial dataset covers large swath of research area and it gives us much more convenient options for data interpretation than traditional maps,it is an ideal data sources for preliminary and feasible study in transportation engineering. However, for the feasibility study of a railway project,the traditional hydrology calculating procedure just uses topographic maps and surveyed data, which makes it more time consuming and inaccurate. So it is necessary to design a more efficient and accurate hydrology calculating approach. Research conclusions :( 1) The new approach applying the various spatial data for hydrology calculating is very effective and feasible. (2) The approach was successfully applied in the drainage design for the feasibility study of the Mieso - DireDawa Railway project in Etliiopia, improving the efficiency and accuracy for hydrology design. ( 3 ) Rather than reviewing and interpretation traditional maps to extract the necessary geographic or runoff parameters,this new approach is more accurate than the traditional method,and is much easier to maintain those dataset through data base manipulation,makingit more applicable for thehydrology calculation of preliminary or feasibility study of railway project.