So far, a number of wetland classification systems have been developed by investigators from different fields. However, general criteria or indexes for the classification are still needed, and quantitative models should be introduced for the purpose of organizing information and describing the similarities or differences among the elements in wetlands. Based on the systematic comparison of existing classification systems, a comprehensive classification system for wetlands is presented in this paper, from which identification at different levels (clan, sub clan, group, class and type) becomes much easier. “Clan” is determined by hydrologic and geomorphologic characteristics, which can be further divided into several “sub clans” according to dynamic controlling factors upon the wetlands; “group” is used for distinguishing the differences of bottom characteristics of wetlands; and “class” is defined in terms of vegetation physiogomy, followed by the more detailed description of “type” demonstrating the immersing features in the wetlands. Furthermore, the new classification system will promote the process of quantitative descriptions of wetland systems.