Objective To analyze the effect of ultrasound‑guided serratus anterior plane block (SAPB) on analgesia in rib fracture internal fixation. Methods Seventy‑eight patients with rib fractures who were treated with internal fixation were selected as subjects. According to the random number table method, patients were divided into a control group and an observation group, with 39 cases in each group. All patients were treated with internal fixation with rib fracture under combined anesthesia. Patients in the observation group were treated with ultrasound‑guided SAPB before anesthesia induction. Patients in the control group were not intervened. The amounts of sufentanil used in the two groups were compared. Heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse oxygen saturation (SpO2) were compared before surgery during surgery and 2 h after surgery. Visual Analogue Scale (VAS) scores before surgery, and 12 h, 24 h and 72 h after surgery were compared between the two groups. At the same time, the dose of butorphanol and incidence of complications were observed in the two groups. Results The amount of sufentanil in the observation group was lower than that in the control group (P<0.05). The heart rate, SBP and DBP of the observation group were lower than those of the control group at 2 h after operation, and the SpO2 was higher than that of the control group at 2 h after operation (P<0.05). The VAS score of the observation group was lower than that of the control group at 2, 12 and 24 h after operation (P<0.05). The dose of butorphanol used in the observation group was lower than that used in the control group (P<0.05). The incidence of postoperative agitation and the incidence of complications in the observation group were lower than those in the control group (P<0.05). Conclusions In the internal fixation of rib fracture, ultrasound‑guided SAPB before anesthesia induction can effectively reduce the dose of sufentanil and postoperative butorphanol, maintain steady postoperative vital signs and reduce postoperative pain. Meanwhile, it can reduce postoperative agitation and complications.