〔Abstract〕 Objective To evaluate the effect of Arthroscopic Treatment of Popliteal Cyst through the modified double posteromedial portal. Methods A total of 210 patients who diagnosed with popliteal cyst between April 2019 and June 2021 were chosen.62 patients underwent surgical treatment, include open excision and arthroscopic surgery.At the same time, 31 patients with conservative treatment were included as conservative treatment group.The Visual Analogue Score(VAS score),Lysholm knee function score, and Knee Society Score(KSS) scores were assessed before and 3 months after the operation. Results In the open excision group, preoperative VAS score was 3.69±0.93,Lysholm score was 63.75±4.76,KSS score was 60.87±5.85,and postoperative VAS score was 2.04±1.04,Lysholm score was 76.81±6.35,KSS score was 70.42±4.87.In the arthroscopic surgery group, preoperative VAS score was 3.81±0.84,Lysholm score was 62.84±4.85,KSS score was 58.95±4.79,and postoperative VAS score was 1.47±0.85,Lysholm score was 82.35±7.34,KSS score was 78.52±5.67.In conservative treatment group, preoperative VAS score was 3.92±1.02,Lysholm score was 61.39±3.92,KSS score was 62.42±6.78,and postoperative VAS score was 3.94±1.14,Lysholm score was 61.85±7.48,KSS score was 60.52±6.37.Significant improvement was observed in all the measurements after the operation compared to before the operation(P<0.001).Compared with the open excision group, the arthroscopic surgery group improved better(P<0.05). Conclusion Arthroscopy through the modified double posteromedial portal in the treatment of popliteal cyst has satisfactory results.