Objective To compare the effect of ultrasound‑guided brachial accessory nerve block in the "horn pocket" area and traditional peri‑plexus block on diaphragmatic palsy. Methods A total of 88 patients who required upper limb surgery below the shoulder joint from January 2018 to December 2019 were selected. According to the random number table method, they were divided into two groups (n=44): a control group and an experimental group. Patients in the control group underwent ropivacaine brachial plexus perineural injection, including 0.375% ropivacaine (5 ml) in the "corner pocket"+15 ml around the plexus. Patients in the experimental group were given ropivacaine under the guidance of ultrasound, including 0.375% ropivacaine (15 ml) in the "corner pocket"+5 ml around the plexus. Then, the two groups were compared for the forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), diaphragmatic mobility during calm breathing and forced breathing, and diaphragmatic paralysis rate after calm breathing and forced breathing before anesthesia and 15 min and 30 min after anesthesia. The time of disappearance of skin pain in the axillary nerve, the musculocutaneous nerve, the ulnar nerve, the radial nerve and the median nerve was measured by acupuncture. The time of anesthesia block, duration of anesthesia and adverse reactions 24 h after operation were recorded. Results Compared with those before both groups presented decreases in anesthesia, FEV1, FVC, diaphragmatic mobility of calm breathing and forced breathing 15 min and 30 min after anesthesia (P<0.05). Then, 15 min and 30 min after anesthesia, the experimental group presented significantly higher FEV1 and FVC than the control group (P<0.05), and higher diaphragm mobility of calm breathing and forced breathing than the control group (P<0.01). After anesthesia, the total paralysis rate of diaphragm in the experimental group was significantly lower than that in the control group (P<0.05). After anesthesia, the time of disappearance of skin pain in the axillary nerve, the musculocutaneous nerve, the ulnar nerve and the radial nerve in the experimental group was lower than that in the control group (P<0.05), and there was no significant difference in the time of disappearance of skin pain in the median nerve between the two groups (P>0.05). The experimental group showed shorter time of anesthesia block, longer anesthesia duration, and a lower total incidence of adverse reactions than the control group, without statistical differences (P>0.05). Conclusions Ultrasound‑guided brachial nerve block in the "corner pocket" area can significantly reduce the rate of diaphragmatic paralysis, improve pulmonary function and shorten the time of neuroanesthesia in the operating area, with good safety.