Objective: To analyze the effect of short-segment circumferential decompression and the nerve function improvement in 30 cases of multilevel thoracic OPLL assisted by intraoperative ultrasound. Methods: A total of 30 patients with multilevel thoracic OPLL from January 2016 to January 2021 were enrolled, all of whom were located by intraoperative ultrasound and underwent circumferential decompression. There were 14 males and 16 females, with an average age of (49.3±11.4) years. The initial symptoms were mainly numbness and weakness of lower limbs (83.3%), and the mean duration of symptoms was (33.9±42.9) months (1-168 months). Neurological function was assessed by the Modified Japanese Orthopedic Association (mJOA) score (0-11) preoperative and at the last follow-up, in which the rate of neurological improvement was calculated by the Harabayashi method. The patients were divided into excellent improved group and poor improved group according to the improvement of neurological function. The age, body mass index (BMI), duration of symptoms, operation time, blood loss, mJOA score, surgical level, and cerebrospinal fluid leakage of the two groups were collected and analyzed for statistical differences. The factors influencing the improvement of neurological function were analyzed by univariate and multivariate Logisitic regression analysis. Results: The mean operation time was 137.4±33.8 (56-190) min, and the mean blood loss was (653.7±534.2) mL (200－3 000 mL). The preoperative mJOA score was 6.0±2.1 (2－9), and the last follow-up mJOA score was 7.6±1.9 (4－11), which was significantly improved in all the patients (P < 0.001). The average improvement rate of neurological function was 38.1%±24.4% (14.3%－100%), including 75%－100% in 4 cases, 50%－74% in 3 cases, 25%－49% improved in 14 cases, and 0%－24% in 9 cases. There was significant difference in intraoperative blood loss between the excellent improved group and the poor improved group (P=0.047). Intraoperative blood loss was also an independent risk factor in regression analysis of neurological improvement. Conclusion: Thoracic circumferential decompression assisted with intraoperative ultrasound can significantly improve the neurological function of patients with multilevel OPLL and achieve good efficacy. The improvement rate of nerve function can be improved effectively by controlling intraoperative blood loss.