Objective To compare the complications of transforaminal intervertebral fusion combined with pedicle screw fixation under the intramuscular approach and oblique lateral intervertebral fusion combined with pedicle screw fixation in the treatment of lumbar spine lesions. Methods The data of 157 cases of lumbar spine lesions admitted from January 2016 to December 2018 were retrospectively analyzed. There were 51 males and 106 females. The age range from 24 to 76 years, averagely (54.4±9.93) years old. Disease types: 33 cases of lumbar disc degeneration, 49 cases of lumbar spinal stenosis, 44 cases of lumbar degenerative spondylolisthesis, 31 cases of lumbar spine arch spondylolysis with or without spondylolisthesis. Lesions: 18 cases of L3/4 and 139 cases of L4/5. According to the time of admission, 81 cases were taken by bilateral pedicle screw fixation under the posterior muscle space approach and interbody fusion and 76 cases by oblique lateral intervertebral fusion combined with bilateral pedicle screw fixation under the posterior muscle space approach. Observed and compared the clinical and imaging results of the two groups, especially the complications. Result The operation time of the two groups was basically the same. The intraoperative bleeding in the oblique lateral fusion group was significantly less than that in the posterior fusion group. The average follow-up time was 20.8±10.77 months. The height of the intervertebral space was recovered well after the operation, but part of them were lost during the follow-up. There were 48 cases of fusion cage subsidence (17 cases in the posterior fusion group, 31 cases in the oblique lateral fusion group). There was no internal fixation loosening or fracture. The balance of the coronal and sagittal planes of the lumbar spine was improved in the two groups. The fusion rate of the posterior fusion group was 96.3%, and 97.4% of the oblique lateral fusion group. The VAS score of low back pain and the ODI index of lumbar spine function also recovered significantly. Complications: No incision infection occurred in the two groups. In the posterior fusion group, there were 2 cases of dural tear and cerebrospinal fluid leakage, 3 cases of pedicle entry point fractures, and 5 cases of endplate injury. There were 2 cases of nerve root injury, 3 cases of partial skin necrosis of the incision, 1 case of poor incision healing, 1 case of fusion cage displacement, and 1 case of reoperation. There were 16 complications in the posterior fusion group, with an incidence of 19.75%. In the oblique lateral fusion group, there were 1 case of segmental vascular injury, 2 cases of sympathetic chain injury, 15 cases of endplate injury, 2 cases of vertebral fracture, 3 cases of postoperative transient iliopsoas muscle weakness, 2 cases of left thigh anterior and lateral pain and quadriceps weakness, 1 case of nerve root injury, 1 case of reoperation, and 1 case of lateral displacement of the fusion cage. A total of 23 complications occurred in the oblique lateral fusion group, with an incidence rate of 31.58%. The complication rate in the oblique lateral fusion group was higher than that in the posterior fusion group, and the difference was statistically significant. Conclusion Transforaminal intervertebral fusion combined with pedicle screw fixation and oblique lateral intervertebral fusion combined with pedicle screw fixation under the intermuscular approach have obtained good clinical results for the treatment of lumbar spine lesions. But due to the difference of two types of surgical spinal canal decompression, the approach of intervertebral fusion, the size and area of the fusion device, the bone graft material, and the location of the fusion device, so the incidence of complications of the two types of surgery is different, and there are obvious differences in the composition of complications.