According to the requirements of subwatershed codification for distributed hydrological models, river and watershed codification methods described in literature were studied. It is found that only five coding methods can meet the requirements of distributed hydrological models: the topological property table coding method (TPTCM), binary-tree coding method (BCM), multi-tree coding method (MCM), Pfafstetter coding method (PCM), and stem-branch topological coding method (SBTOPO). The advantages and the disadvantages of the five methods were examined based on analysis of their coding rules. The second Songhua River was selected as the study area for subwatershed division and codification. The results show that the TPTCM, MCM, and SBTOPO are superior to the other two methods in one-way and multi-way confluence situations. The TPTCM can directly find and obtain the codes of adjacent inflow and outflow subwatersheds, and the BCM and SBTOPO can directly calculate their codes, but the PCM and MCM obtain their codes by searching the entire coding system. The PCM and SBTOPO are better than the other three methods in terms of analysis of the upstream and downstream relationships between any two subwatersheds. All five coding methods have their own advantages and disadvantages. A suitable coding method should be selected according to research contents and coding requirements of distributed hydrological models in practical applications.