Objective: To introduce the surgical technique and preliminary clinical effect of a modified arthroscopy technique in the treatment of lateral meniscus cyst of knee joint. Methods: Retrospectively analyzed from January 2017 to December 2018, admitting in our department for the treatment of lateral meniscus cyst. A total of 120 cases were treated with a modified arthroscopy technique：resection the lower surface of the meniscus of teared meniscus to drain cyst fliud,and trans-synovial cyst wall tissue completely resection.Lysholm knee function score and Tegner score used for clinical knee function evaluation, and MRI within 3 days after surgery and at the last follow-up was used to evaluate the recurrence of cysts. Results: 120 patients were mean followed up for 34months. Postoperative MRI showed cyst has been completely resected in 115 cases (95.8%). The last follow-up MRI showed no cyst recurred in all patients including the 5 cases of whose cyst were still part existed. Lysholm scale and Tegner score at the last follow-up were respectively (88.82±3.46)、(5.92±0.72), compared with preoperative (56.21±7.51)、(3.74 ±64), were statistically significant (T1 = 47.99, P < 0.001;T2 = 57.33, P < 0.001). Conclusion: The modified arthroscopy technique in the treatment of lateral meniscus cyst of knee joint can maximize the resection of cyst and cyst wall tissue, the postoperative knee joint function recovers well, and the postoperative recurrence rate is low, which is worthy for clinical application.