To investigate the characteristics of the spinal-pelvic sagittal sequence in patients with lumbar vertebral posterior ring apophysis separation (PRAS). A retrospective analysis was conducted on 119 hospitalized patients with PRAS, and 119 adults without symptoms of low back and leg pain were selected as the control. General data and spinal-pelvic sagittal parameters were collected and analyzed. Compared to the control group, the pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis (TK) of the PRAS group were significantly lower, while the pelvic tilt (PT), sagittal vertical axis (SVA), and pelvic incidence minus lumbar lordosis (PI-LL) were significantly higher. There was no significant difference in thoracolumbar kyphosis (TLK) between two groups. In patients with PRAS, the LL value of lumbar curvature was moderately correlated with TK and SS, while PI, PT, and SS were pairwise correlated, indicating that the change in one parameter is often accompanied by simultaneous changes in other parameters if PRAS happens. The correlation between different parameters could provide guidance for the diagnosis of PRAS. In terms of lumbar lordosis type, PRAS group was mainly of Roussouly type I, while the control group was mainly of type II, and the difference in the composition ratio was statistically significant. As reflected by the spinal-pelvic sagittal parameters, the patients with PRAS exhibited reduced thoracic and lumbar curvature, posterior pelvic tilt, and fewer vertebral bodies involved in lumbar lordosis. These morphological characteristics indicate the changes of the mechanical structure of the spine.