Risk assessment of water resources system is the key to ensure the security and sustainable utilization of water resources.Aiming at the issues existing in the development and utilization of water resources in the Sanjiang Plain,such as low rates of water resources development and utilization,water shortages,and imbalance between supply and demand,the observation-control risk model was applied to perform risk assessment of water resources carrying capacity of eight regions in the Sanjiang Plain.According to the synchronized analysis of risk and gain,the degree of water resources carrying capacity of each study area was determined,and the corresponding management measures were proposed.The research results can provide important theoretical basis for formulating scientific and reasonable water resources sustainable utilization strategy in the Sanjiang Plain,and also open up a new way for the research in the field of risk assessment of water resources system.