Taking surface runoff of Coastal Highway in Liaoning Province as research object, this paper analyzed water quality characteristics of runoff and flow rules of pollutants. It proposed using constructed wetland treatment technique in the drainage system from the perspective of effectively removing major pollutants. Using the constructed wetland k-C* model and relevant experience, parameters of constructed wetland can be obtained. The basic model is as follows: constructed wetland lies in two sides of the road, and surface runoff sewage is collected and treated separately with 1 km road section as the collection unit. The wetland area in one side is 191.6 m2, average water depth is 0.5 m, wetland width is 8 m, and wetland length is 24 m.