Abstract: Wetlands play an important role in watershed hydrological processes that underlie a range of potential ecosystem services. A solid understanding of watershed hydrological regulation functions provided by wetlands, i.e., supporting watershed water balance, attenuating flood and drought risks, and mitigating climate change, is extremely meaningful for reaching sustainable wetland and water resources management. This paper provides a thorough review of the hydrological regulation functions of watershed wetlands. It addresses the definition and connotation of hydrological regulation functions of watershed wetlands as well as their three principal characteristics, namely spatiotemporal variation, threshold effects, and multidimensional nature. The internal driving factors of the functions include soil properties, vegetation characteristics and initial hydrological conditions, and the external factors are watershed characteristics, rainfall patterns, climate change, and anthropogenic activities. The methodology and available hydrological models for quantifying hydrological regulation functions of watershed wetlands are systematically summarized and discussed. Finally, considering discipline development and manage requirements of ecohydrology theory, we highlight specific research gaps and barriers that need to be filled in hydrological regulation functions of watershed wetlands.