Objective Our study aims to identify the median effective concentration (EC50) of ropivacaine in the ultrasound‑guided brachial plexus block through costoclavicular space. Methods Forty patients from June 2018 to February 2019 with hand fracture were selected and were given an ultrasound‑guided brachial plexus block. Sequential administration of ropivacaine was performed with an initial concentration 0.33%. The adjacent volume gradient is 0.02% with a total volume of 22 ml. The sensorimotor function was measured 30 min after drug administration. The patient with 2‑level sensory and 2‑level motor block was considered as successfully anesthetized. Once the case was considered as effective, the next patient would be given a lower gradient concentration of ropivacaine. Otherwise, the next patient would be given a higher gradient concentration of ropivacaine until we got 7 inflection points.Probability regression method was adopted to calculate the EC50 and the 95% confidence interval (CI) of ropivacaine employed in the ultrasound‑guided brachial plexus block through costoclavicular space in patients with hand fractures. Results Of the 40 patients, 21(55%) were successfully blocked, and the EC50 of ropivacaine was 0.23% (95%CI 0.21%‒0.26%). Conclusions The EC50 of ropivacaine is 0.23% in the ultrasound‑guided brachial plexus block through costoclavicular space in patients with hand fractures.