Objective To analyze the feasibility and safety of ultrasound-guided continuous femoral nerve block in senile total knee arthroplasty (TKA), and to provide reference for postoperative analgesia of lower limb surgery. Methods 79 senile patients with unilateral TKA in the hospital from August 2016 to November 2018 were selected, and they were divided into control group (40 cases) and research group (39 cases) by random number table. Control group was given postoperative patient-controlled intravenous analgesia, while research group was given ultrasound-guided continuous femoral nerve block. The incidence of adverse reactions during analgesia was recorded. The analgesic effects were evaluated by postoperative visual analogue scale (VAS) on postoperative 4h, 8h, 12h and 24h rest state, 48h and 72h passive motion state. At the time of connection of analgesia device (T0), after connection for 12h (T1) and after connection for 48h (T2), the hemodynamics indexes [heart rate (HR), oxygen saturation (SpO2), mean arterial pressure (MAP)] and hemorheology indexes were detected and recorded. Results The pressing number of patient-controlled analgesia in research group was less than that in control group, the incidence of nausea and vomiting in research group during analgesia was lower than that in control group (P<0.05); At each time after surgery under rest sate or passive motion state, the VAS scores of research group were lower than those of control group (P<0.05); At each time after surgery, there was no statistical difference in the levels of MAP and SpO2 between the two groups (P>0.05); There was no statistical difference in the HR between the two groups at T0 (P>0.05), the levels of HR in the two groups at T1 and T2 were higher than those at T0, but the increased range of research group was lower than that of control group (P<0.05); There was no statistical difference in the levels of hemorheology indexes between the two groups at T0 (P>0.05); The plasma viscosity, whole blood high-shear viscosity and whole blood low-shear viscosity in control group at T1 and T2 were higher than those in research group (P<0.05). Conclusion Ultrasound-guided continuous femoral nerve block in senile TKA has better analgesic effects, it can stabilize hemodynamics, have less effect on hemorheology, achieve less adverse reactions, enhance surgical effects and promote postoperative rehabilitation.