Objective To analyze radiological changes of femoral condylar cartilage kissing lesion after anterior cruciate ligament (ACL) reconstruction using magnetic resonance(MRI) T2 Mapping technique. Methods From June 2013 to July 2015, 39 cases(37 male, 2 female) who accept ACL reconstruction were included. All the patients accept MR scan before operation and at 3 months, six months, 1 year after surgery. The technique of MR scan were: Routine 2D-MRI (coronal TSE-T2WI, sagittal TSE-T1WI, sagittal TSE-PDWI sequence) and 3D-MRI (sagittal TSE-3D-SPCFS sequence) scan. Mapping T2 scan is performed based on gradient echo sequence after complete scanning.Measurement items included: assessment of the ICRS(International cartilage repaire sociaty) Grading, cartilage thickness and T2 value of the kissing lesion site femoral condyle. Results The ICRS Grading was significantly reduced (χ2=6.317, P=0.042) at three months postoperatively compaired with initial injury. However, the grading of three months and six months comparison(χ2=4.452, P=0.108),and six months to one year comparison(χ2=5.638, P=0.058) had no significant difference.In the followup time,cartilage thickness of the kissing lesion site had no significant change among all periods(front: F=0.067 P=0.797, middle: F=0.086 P=0.832, back:F=0.073 P=0.688 ).In T2 Mapping measurement: Kissing lesion revealed continuous articulation but imcomplete cartilage.In T2 mapping image the local signal mixed uneven and gradations of color is orange or red, T2 value increased significantly. However, there was no significant difference in the preoperative and postoperative values of T2 Mapping (F=0.375, P=0.093). Conclusion Mapping T2 technique can effectively evaluate the changes of cartilage injury combined with anterior cruciate ligament injury. 3 months after surgery, the edema of the bone marrow was gradually disappeared, but there was no significant change in cartilage thickness and T2 value.