Objective To investigate the clinical effect of adductor magnus tendon transposition with arthroscopic in reconstruction medial patellofemoral ligament (MPFL) for the treatment of patellofemoral joint instability of adolescents. Methods Eighteen juvenile patients (21 knees) with patellofemoral joint instability (including chronic patellar dislocation and recurrent patellar dislocation) were treated with adductor magnus tendon transposition for MPFL reconstruction, combined with lateral patellofemoral ligament release. They were followed up for 12- 30 months. The complications, patellofemoral angles and Lysholm scores before and after operation were recorded and compared. Results There was no complications such as wound infection, redislocation, patellofemoral joint instability and epiphyses injured. All patients got excellent knee flexion and extension function. Patella fear tests were all negative. The patellofemoral angles and Lysholm scores after operation were improved significantly than those before operation:(10.3 ± 4.1)° vs. (-3.8 ± 4.9)°, (92.7 ± 3.6) scores vs. (61.5 ±2.4) scores, P<0.01. Conclusions Adductor magnus tendon transposition with arthroscopic in reconstruction MPFL can significantly improve the stability of patellofemoral joints. This is one of the effective methods for the treatment of patellofemoral joint instability of adolescents.