Railway washing wastewater, containing a large number of carbohydrates, fat, protein, cellulose, and other organic pollutants, will cause serious pollution, result in production of foul-smelling matter, impact on the survival of aquatic life and hinder the sustainable development of railway transport, if the wastewater is directly discharged into the nature water body. At present, the main treatment processes for railway washing wastewater are physical and chemical treatments which are inefficient, unstable and expensive and can not meet the requirements of water recycling, so a treatment process suitable for railway washing wastewater is badly in need of research and development. The constructed rapid infiltration (CRI), an ecological wastewater treatment technology, excels at treating wastewater especially toward CODcr，BOD5 and SS. But the efficiency of TP removal in CRI is inefficient. In order to improve efficiency of TP removal, sponge iron is added to the traditional CRIs. To determine the feasibility of railway washing wastewater disposal by CRI, the washing waste water of Chengdu Railway Administration was selected as test sample. Traditional CRIs and improved CRIs were applied to treat the washing waste water and degradation kinetics characteristics of TP were studied, the results show that: when average TP concentration of inflow is 6.24mg/L, in traditional CRIs and improved CRIs, average TP concentration of outflow are 4.17mg/L and 1.40mg/L respectively, average efficiency of phosphorus removal are 33.03% and 77.50% respectively; as the TP concentrations of inflow increase, TP concentrations of outflow increase accordingly but the removal rates of TP are stable. Because of addition of sponge iron, the removal rate of TP in improved CRIs is more 44% than traditional CRIs. The results of this experiment show that: Improved CRI is a clean, cheap and ecological technology which is suited for the railway washing wastewater treatment and can promote the sustainable development of traffic engineering, reduce the negative impact on the ecological environment and make railway traffic compatible with resources, environment and social economy.