Objective To evaluate the clinical results of fibrin matrix-mixed gel-type ACI (G-ACI)during postoperative cartilage repair.Methods A 48-year-old female patient who had cartilage defects in the patella (1.8 cm×3.0 cm) and medial condyle (0.5 cm×0.5 cm) was selected. Both defects belonged to Outerbridge/ICRS Ⅲ-Ⅳ. We began by harvesting 50 mg cartilage from the non-bearing region and had it cultured at the GMP lab of the General Hospital. After 6 months, the autologous chondrocytes and gel scafford were implanted into the defective region by arthrotomy. T1 Vibe MRI, T2 Mapping MRI and Knee Injury and Osteoarthritis Outcome Score (KOOS) were used to evaluate the result of clinical rehabilitation in 6 mon, 1 y and 1.5 y postoperatively.Results The earliest signs of proliferation of chondrocytes in the transplant area were seen 6 mon postoperatively as shown by T1 Vibe MRI. Newborn chondrocytes filled the transplant area completely till 1.5 years after operation. T2 Mapping MRI showed a reconstruction process of newborn chondrocytes. T2 Mapping values decreased after operation. All the items in KOOS progressively improved after G-ACI operation, but faster recovery occurred between six months and one year postoperatively.Conclusions G-ACI can reduce surgical difficulties without cutting and suturing while facilitating attachment, thus it can be easily performed under arthroscopy regardless of the site, shape and depth of defects. We have achieved good outcomes postoperatively during early follow-up. G-ACI appears to be a safe and effective method to repair cartilage defects of knees.