Objective To investigate the risk factors of facet joint excessive resection and its influence on effectiveness after the treatment of degenerative lumbar diseases under large-channel endoscope. Methods The clinical data of 212 patients with degenerative lumbar diseases treated with large-channel spinal endoscopic technology between June 2022 and June 2024 were retrospectively analyzed. Among them, 120 were male and 92 were female. The age ranged from 18 to 85 years, with an average of 54 years. According to the facet joint resection rate measured by CT after operation, the patients were divided into preservation group (facet joint preservation rate≥50%) and excessive resection group (facet joint preservation rate<50%). Visual analogue scale (VAS) score for low back and leg pain, Oswestry disability index (ODI), and Japanese Orthopaedic Association (JOA) scores were used to evaluate the improvement of pain and function before operation, at 1 month after operation, and at last follow-up, and the modified MacNab criteria were used to evaluate the effectiveness at last follow-up. The occurrence of lumbar instability was observed during follow-up. Univariate analysis was performed on variables including gender, age, body mass index, responsible segment, surgical side, whether over-top decompression was performed, whether presence of lateral recess stenosis, whether presence of intervertebral disc calcification, whether presence of lumbosacral transitional vertebrae, whether presence of facet joint hyperplasia, and imaging parameters [facet joint angle (FJA), laminar lateral-oblique angle, maximum width between the medial and lateral margins of the superior articular facet on axial CT (d1), distance between the base of the ipsilateral spinous process and the midline of the facet joint at the responsible segment (d2), as well as the width (d3) and height (d4) of the interlaminar space at the responsible segment on anteroposterior X-ray films] between the preservation group and the excessive resection group. And logistic regression analysis was further used to identify risk factors for facet joint excessive resection. Results All patients underwent operative procedures successfully, and all incisions healed by first intention. No complication such as vascular and nerve injury, infection, and spinal cord hypertension-like syndrome occurred. There were 55 patients enrolled in the excessive resection group, and 157 patients in the preservation group. All patients were followed up 12-36 months, with a mean of 23.5 months. There was no significant difference in low back pain VAS score, leg pain VAS score, ODI, and JOA score between the two groups preoperatively (P>0.05). The low back pain VAS score, ODI of the excessive resection group were significantly higher than those of the preservation group, and JOA score was significantly lower at 1 month after operation (P<0.05), and there was no significant difference in the above indicators between the two groups at other time point (P>0.05). At last follow-up, the effectiveness evaluated according to the modified MacNab assessment criteria was no significant difference between two groups (Z=4.270, P=0.118). During the follow-up, 5 cases occurred lumbar instability in the excessive resection group and 4 cases in the preservation group, there was no significant difference between two groups (χ2=2.831, P=0.092). Univariate analysis showed that there were significant differences between the two groups in terms of age, gender, responsible segment, whether presence of lateral recess stenosis, FJA, d1, d2, laminar lateral-oblique angle, and d3 (P<0.05). Further logistic regression analysis showed that female patients, presence of lateral recess stenosis, FJA (≤45°), d2 (≤11 mm), d3 (≤21 mm) were risk factors for excessive resection of facet joint (P<0.05). ConclusionThe incidence of excessive resection of facet joint in lumbar degenerative diseases treated by large-channel endoscopic depression reached 25.94% (55/212), and excessive resection of facet joint affects the recovery of lumbar pain and function in the short term after operation. Female patients, lateral recess stenosis, and FJA (≤45°), d2 (≤11 mm), d3 (≤21 mm) are risk factors for excessive resection of facet joint, which should be paid attention to in order to reduce the incidence of excessive resection of facet joint.