The whole process of the scheme design for the rainwater and sewage separation reconstruction in the old county town of Jingyang County in Shaanxi Province is firstly introduced, including the contents of the pipeline survey, drainage pipeline inspection, scheme design, etc. Then starting from the analysis of the current pipelines, the current pipelines should be used as much as possible to maintain the consistency between the current pipelines and the regional special planning. The impacts on the traffic, environment and current urban areas are comprehensively considered in the design scheme, are solved one by one from the perspective of technology. The results provide some reference for the similar projects.