Abstract:[Objective] To explore the reasons and clinical outcomes of revision hip arthroscopy. [Methods] From June 2015 to Decem- ber 2019, a total of 359 patients underwent hip arthroscopy in our hospital. Of them, 26 patients received revision hip arthroscopy, account- ed for 7.24%, for varying extent of pain and activity limitation before the revision surgery, which lasted for 3~36 months, (15.88±8.04) months on an average, after initial surgery. The revision hip arthroscopy was conducted to identify the cause of the symptoms and give ap- propriate treatment. [Results] As findings of revision hip arthroscopy among the 26 patients, residual deformities of femoroacetabular im- pingement (FAI) were seen in 21 patients, accounted for 80.77%; osteoid osteoma misdiagnosed as FAI in the primary operation in the other hospital was noted in 2 patients, accounted for 7.69%; recurrent synovial chondroma was found in 1 patient, accounted for 3.85%; heterotop- ic ossification was in 1 case, accounted for 3.85%; and recurrent pigmented villonodular synovitis was in 1 case, accounted for 3.85%. All the 26 patients had revision hip arthroscopy performed successfully without serious complications, such as hip dislocation, fracture, infec- tion and others. The follow-up period lasted for 12~26 months, with a mean of (17.54±4.24) months after the revision. The FADIR test, FABER test, and rolling test significantly improved in all the 26 patients at the latest follow-up compared with those before revision (P< 0.05) . In addition, the ROMs, including internal rotation at 0° of flexion, the external rotation at 0° of flexion, internal rotation at 90° of flex- ion, the external rotation at 90° and hip flexion, as well as the mHHS and the IHOT12 scores significantly increased (P<0.05) , whereas the VAS score for pain significantly decreased at the latest follow-up compared with those before revision surgery (P<0.05) . In term of radio- graphic evaluation, the α angle decreased and the femoral head-neck offset increased significantly at the latest follow-up compared with those before revision (P<0.05) , whereas the LCEA remained unchanged in the 26 patients (P>0.05) . [Conclusion] The main causes of revi- sion hip arthroscopy include residual FAI, misdiagnosis and recurrence of diseases. On the premise of correct preoperative diagnosis and mature surgical techniques, revision hip arthroscopy does still achieve good clinical outcome.