Objective To explore the potential trajectory categories and influencing factors of acute postsurgical pain (APSP) in patients undergoing open lumbar fusion surgery,to analyze the influencing factors of different potential categories, and to provide theoretical basis for developing targeted analgesic measures for patients of different categories in the future. Methods A convenience sampling method was utilized to select 251 patients undergoing open lumbar fusion surgery. Social-demographic data, pain scores, and sleep quality assessments were collected one day before surgery, with pain levels assessed at nine time point spost-surgery(0 h, 6 h, 12 h, 1 d, 2 d, 3 d, 4 d, 5 d, and 6 d of extubation). Latent class growth modeling was employed to identify distinct APSP trajectories, and logistic regression was used to analyze predictive factors of these trajectories. Results Three distinct APSP trajectories were identified:the pain-aggravation-then-relief group (33.0%),the pain-aggravation-stabilization-then-rebound group (12.0%), and the mild pain group (55.0%). Logistic regression analysis indicated that, compared with the mild pain group, those aged ≤50 years, with sleep disorders, without using postsurgical patient-controlled intravenous analgesia, were more likely to join membership of the pain-aggravation-then-relief group;those with disease duration ≥10 years, education level below high school, operation duration >240 minutes were more likely to join membership of the pain-aggravation-stabilization-then-rebound group (all P<0.05). Conclusion Patients undergoing open lumbar fusion surgery exhibit diverse APSP trajectories. Medical professionals should be attentive to patients who are aged≤ 50, who have disease duration≥10 years, education level below high school, preoperative sleep disorder, operation duration >240 min, and who don’t use postoperative analgesia, and provide timely pain management and intervention.