Objective:To evaluate the clinical efficacy of microfat on neck wrinkles and its structure and viability.Methods:A retrospective analysis was conducted to review the clinical data of 23 patients with neck wrinkles corrected by microfat injection from June 2018 to June 2021 at the Body Contouring and Fat Grafting Center, Plastic Surgery Hospital, Chinese Academy of Medical Sciences, aged (38.1±10.7) years old. A blunt cannula with multiple side holes of 0.8 mm was used to obtain fat particles under low negative pressure and to prepare the microfat by washing and soft centrifugation. A 26-gauge sharp needle was used to inject microfat with small amount and at multiple points into the intradermal and subdermal layer where the neck lines were linearly depressed. Regular follow-ups were carried out after the operation, and the efficacy of the operation was evaluated from routine neck examinations, third-party doctor′s grade scoring and patient′s scoring towards satisfaction. To clarify the structure and viability of microfat, scanning electron microscope was used to observe the structure of fat particles, Calcein-AM/propidium iodide (Calcein-AM/PI) staining to detect tissue viability and Musecell counting to count SVF cells.Results:All of the 23 patients successfully completed the operation without complications such as infection and fat liquefaction. After a follow-up of 3 to 30 months, the neck wrinkles were effectively improved. The postoperative grade scores of third-party doctor was significantly reduced ( P<0.05). And the satisfaction of patients was high, with 20 cases (87.0%) satisfied. Scanning electron microscopy showed that the fat granule cells were tightly arranged and the structure remained intact. Calcein-AM/PI staining showed that most cells in the granules survived. The number of viable SVF cells in fat particles was (9.34±2.68)×10 5/ml. Conclusions:Microfat is easy to obtain with high tissue activity, which is suitable for neck wrinkle filling. Good effects can be achieved with high patients′ satisfaction. It is worthy of clinical application.