Objective To observe the effect of ropivacaine with equal dose and different concentration on continuous femoral nerve block after total knee arthroplasty for elderly people. Methods 180 elderly patients undergoing elective operation of unilateral knee replacement under general anesthesia in The First Affiliated Hospital of Hebei North University from April 2017 to April 2019 were randomly divided into low concentration group (group A), medium concentration group (group B) and high concentration group (group C), with 60 cases in each group. Continuous femoral nerve block was used in all the three groups. In group A, 0.15% ropivacaine was used in the analgesic pump with a background dose of 4ml#h, in group B, 0.2% ropivacaine was used in the analgesic pump with a background dose of 3ml#h, and in group C, 03% ropivacaine was used with a background dose of 2ml#h. The pain score, muscle strength and MMSE score were observed and recorded in all the three groups at different time after operation. Results VAS score of all patientswas the highest 12 hours after operation. The effects of rest pain and exercise pain in group A were better than those in group B and C (P < 0.05). The muscle strength of quadriceps femoris in group A was significantly higher than that in group B and C (P < 0.05). The MMSE scores of all groups were significantly lower than the basic values, and group A was significantly higher than group B and group C on the third day after operation (P < 0.05).Conclusion Low concentration and high volume of local anesthetics are more beneficial to the recovery of pain relief, muscle strength and cognitive function in elderly patients after TKA operation.