Hemoglobin concentration,as an important indicator of the recovery of the surgical site of the flap graft, can reflect the state of blood circulation.Current methods for monitoring blood flow after surgery are limited to physical observations and empirical diagnosis of skin temperature,color and sw elling,or only rough determination of oxygen saturation,and less to real-time monitoring of hemoglo bin concentration.In this paper,a multi-directional reflective non-invasive test system for detecting hemoglobin concentration after skin flap transplantation is designed and constructed.Through the collection and analysi s of sample data,a correction factor is introduced to achieve non-invasive detection of hemoglobin concentra tion.The experimental results show that the standard deviation of 10consecutive measurements of 6volunteers is relatively small;the correlation between 40measurement values and true values is relatively strong;t he concentration of hemoglobin collected after skin heating is sensitive to temperature changes,indicating tha t the system has good stability, accuracy and effectiveness.The project team will cooperate with the Huaihe Hosp ital of Henan University to conduct clinical testing of hemoglobin concentration in patients after flap tran splantation,further calibrate the data and develop miniaturized portable measuring instruments to provide more reliable basis for postoperative care.