Objective:To observe the therapeutic effect ofcapsaicin at different concentrations on chronic knee arthritis pain model in mice.Methods:Choosing 50 healthy adult male Kunming mice builded chronic knee arthritis pain model by injecting 0.01 mL CFA (Complete Freund's Adjuvant,CFA) into left joint cavity.The model would be succeed in building after 3 weeks.The successful model mice were divided into five groups randomly (n=10):The first experimental group (saline group),the second experimental group (capsaicin excipient group),the third experimental group (0.5 ％ of capsaicin),the fourth experimental group (3 ％ of capsaicin) and the fifth experimental group (8 ％ of capsaicin).All of the mice would be observed the time of withdrawal latencies from the thermal heated surface after administration of one,four and seven hours,and thermal withdrawal time within 60 days after the injection.Results:①The physiological saline group compared with excipient group,the thermal withdrawal time had no statistically significant difference (P＞0.05)after administration of one,four and seven hours,and thermal withdrawal time within 60 days.②The acute pain duration of the third group would disappear after capsaicin injection 7 hours,four hours for the fourth group,and one hour for the fifth group.③The duration of analgesia of the third group,lasted for 18.9± 1.1 days;The analgesia time of the fourth group lasted for 33.7± 1.0 days;The analgesia time of the fifth group lasted for 58.2± 1.2 days.Conclusions:Capsaicin has analgesic effects on chronic knee pain model in mice induced by CFA,and the days of analgesia increases with the concentration of capsaicin.