Abstract: Objective To determine the dose-response relationship of ropivacaine for brachial plexus block in frozen shoulder guided by ultrasound. Methods One hundred frozen patients,aged 43-71 years,duration of 2 months-5 years,undergoing shoulder lysis under brachial plexus block guided by ultrasound,were randomly divided into 5 groups (n=20 each) using a random number table:group R₁-R₅.Interscalene brachial plexus root positions were determined guided by ultrasound,mixing liquid 0.10%(group R₁),0.15%(group R₂),0.20%(group R₃),0.25%(group R₄),0.30%(group R₅),mecobalamin injection 0.5 mg,betamethasone 1 ml and 0.9% saline total 10 ml were injected into the brachial plexus around.The onset time of anesthesia,pain disappeared time,duration of analgesia,incidence of adverse reactions,before and after treatment pulse oximetry were recorded,and the treatment were evaluated.The response to ropivacaine for brachial plexus block was defined as positive when pain disappeared time was more than 10 min.The ED₅₀,ED₉₅ and 95% confidence interval (CI) of ropivacaine for brachial plexus block guided by ultrasound were calculated by probit analysis. Results The onset time of anesthesia and pain disappeared time shortened,duration of analgesia prolonged,following ropivacaine concentration gradient increasing,the difference was statistically significant (P<0.05).The effective rate (cure and improvement) of the treatment was 100%,no significant adverse reactions occurred.The ED₅₀ and ED₉₅(95%CI) of ropivacaine for brachial plexus block guided by ultrasound were 0.167%(0.153%-0.180%) and 0.217%(0.199%-0.251%),respectively. Conclusion Ropivacaine for brachial plexus block guided by ultrasound is effective for frozen shoulder,with no significant adverse reactions.The ED₅₀ and ED₉₅ of ropivacaine for brachial plexus block in frozen shoulder guided by ultrasound were 0.167% and 0.217%,respectively.