The paper elaborates on the principle, idea and overall architecture adopted in the design of Decision Support System(DSS) for primary health care service. By taking diabetes as a case, the DSS for primary level with functions of diagnosis assistance, risk evaluation, disease management and dual referral has been developed, which can assist primary care physician in preventing, evaluating and treating diabetes. Such a system is of great significance for realizing the management of residents by level and classification as well as providing personalized treatment.