Objective:To explore the optimum opportunity for lumbodorsal muscles exercises of patients undergoing posterior lumbar decompression and instrumentation, and investigate its effect on the rehabilitation outcomes and kinesiophobia.Methods:A randomized controlled trial was used. By convenient sampling method, a total of 120 lumbar disc herniation patients were prospectively selected from Affiliated Nantong Hospital of Shanghai(Nantong Sixth People′s Hospital) from February 2020 to December 2021. The paitients were assigned to early group, middle group and late group, with 40 cases in each group. All patients were given routine postoperative care and lumbodorsal muscles exercises. The early group started to exercise 10th day after operation, the middle group started to exercise 3 weeks after operation, and the late group started to exercise 6 weeks after operation. The intervention effect was respectively evaluated by Japanese Orthopaedics Association (JOA) and Tampa Scale for Kinesiophobia (TSK).Results:There were 3, 1 and 1 missing cases in the early, middle and late group respectively, the age in the 3 groups were (56.05 ± 11.77), (57.33 ± 14.64) and (54.23 ± 15.73) years old in turn. Three months after exercising, the total score of JOA in the early, middle and late group were (25.32 ± 2.45), (24.44 ± 2.19) and (22.13 ± 1.58) in turn, the difference was significant ( F=23.64, P<0.05); the score of TSK in the early, middle and late group were (37.95 ± 6.81), (34.18 ± 6.39) and (33.33 ± 7.36) in turn, the difference was significant ( F=4.82, P<0.05). Conclusions:Lumbodorsal muscles exercises start at 3 weeks after operation can significantly improve the rehabilitation outcome of lumbar disc herniation patients undergoing posterior lumbar decompression and instrumentation, and will not increase the level of kinesiophobia, its can be consider as optimum opportunity for lumbodorsal muscles exercises.