Objective: To explore the effect of preemptive analgesia with hydromorphine on the level of plasma free fatty acids in patients with non-long bone fracture surgery. Methods: Sixty patients with clavicular fractures who were admitted to Baotou Central Hospital for elective open reduction and plate internal fixation under general anesthesia were selected. Randomized into two groups, patients in the observation group were were slowly injected with hydromorphone 30 μg / kg intravenously 15 min before the skin incision, while the patients in the control group were slowly injected with the same amount of normal saline intravenously 15 min before the skin incision. Observation indicators: mean arterial pressure (MAP) and heart rate (HR) at 5 min after entering the operating room (T0), skin incision (T1), 30 min after operation (T2) and 30 min after extubation (T5); the levels of plasma free fatty acid (FFA), norepinephrine (NE) and epinephrine (E) at T0, T2 and T5; VAS scores at 5 min (T0), 5 min (T3), 10 min (T4) and 30 min (T5) after extubation; the incidence of postoperative respiratory depression, nausea and vomiting, skin itching and emergence agitation. Results: There was no significant difference in ASA classification, BMI, gender, age, height, weight, VAS score, MAP, HR and plasma NE, E and FFA levels between the control group and the observation group at T0 (P＞0.05). The MAP and HR in the observation group were lower than those in the control group at T1, T2 and T5 (P＜0.05). The levels of plasma NE, E and FFA in the observation group were lower than those in the control group at T2 and T5 (P＜0.05). The VAS scores of the observation group were lower than those of the control group at T3, T4 and T5 (P＜0.05). There was no significant difference in the incidence of nausea and vomiting, skin itching and respiratory depression between the two groups (P＞0.05). The incidence of emergence agitation in the control group was higher than that in the observation group (P＜0.05). Conclusion: Preemptive analgesia with 30 μg/kg hydromorphone in non-long bone fracture surgery can effectively reduce postoperative pain, reduce perioperative stress and hemodynamic fluctuations, stabilize plasma free fatty acid levels. At the same time, it can effectively reduce the emergence agitation and does not increase the incidence of postoperative respiratory depression, skin itching, nausea and vomiting and other adverse reactions.