Objective:To investigate the effect of early ambulation time on lower limbs muscle strength and fear of falling in patients with total knee arthroplasty, so as to provide basis for promoting the postoperative rehabilitation of patients undergoing total knee arthroplasty.Methods:A total of 210 patients after unilateral total knee replacement from July 2018 to December 2019 in the Second Affiliated Hospital of Soochow University were included and assigned to experimental group 1, experimental group 2 and experimental group 3 by random digits table method, each group contained 70 cases, and the patients began ambulation at 16, 20, 24 hours after knee replacement, respectively. The peak torque (PT) of knee joints flexors and extensor as well as hamstrings quadriceps ratio (H/Q) were compared among three groups at 1 week, 1 month and 3 months after knee replacement. The fall efficiency was evaluted by Modified Fall Efficacy Scale (MFES), the fear of falling rate was conducted by single item method.Results:After 1 month of knee replacement, the PT of knee joints flexor and extensor and H/Q were (18.73±5.49) N·m, (37.56±7.76) N·m, (48.08±9.19)% and (18.44±5.27) N·m, (37.04±7.07) N·m, (47.49±9.30)% in the experimental group 1 and experimental group 2, which were higher than those in the experimental group 3(16.38±2.85) N·m, (33.75±6.75) N·m, (43.48±7.17)%, the differences were statically significant ( t values were 2.316-3.057, P<0.05). After 1 week of knee replacement, the fear of falling rate were 72.3%(47/65) and MFES scores were (3.14±0.58) points in the experimental group 1, 53.7%(36/67), (3.81±0.65) points and 50.8%(32/63), (3.87±0.74) points in the experimental group 2 and experimental group 3, the fear of falling rate significantly increased and MFES scores significantly decreased in the experimental group 1 compared to the experimental group 2 and experimental group 3, the differences were statistically significant ( χ2 values were 5.780, 4.878, t values were 6.221, 6.129, P<0.05). Conclusions:Twenty hours after knee replacement is the best time for ambulation, which can shortern the time for lower limbs muscle strength recovery and reduce the risk of fear of falling.