Objective To explore the analgesic effect of dexmedetomidine （DEX） combined with ropivacaine （ROP） bilateral subcostal transversal plane （TAP） block on open hepatectomy. Methods A total of 100 patients with open hepatectomy admitted to our hospital from January 2021 to December 2022 were selected as study subjects and randomly divided into ROP group （n=50） and ROP+DEX group （n=50）. All patients received endotracheal intubation, followed by a bilateral subcostal block with ultrasound guidance. The ROP group was given 0.375% ropivacaine 40 mL.The ROP+DEX group was given ropivacaine combined with dexmedetomidine （1 g/kg）. Afer hepatic resection was completed, intravenous patient controlled analgesia （PCIA） was given before wound suture. Hemodynamics parameters such as heart rate and mean arterial pressure, analgesic effect, and adverse reactions were observed and compared between the two groups. Results The heart rate and mean arterial pressure in the ROP+DEX group were significantly lower than those in the ROP group at 30, 60 and 120 min after surgery （P<0.05）. The first complaint of pain in the ROP+DEX group was later than that in the ROP group （P<0.01）. The VAS scores of the ROP+DEX group were significantly lower than those of the ROP group at 2 and 6 h after surgery （P<0.01）. There was no significant difference in the overall incidence of adverse reactions between the two groups within 24 h after surgery （P>0.05）. Conclusion ROP combined with OEX TAP block for open liver resection under both costal margins has obvious analgesic effect, which can significantly prolong the analgesic time and reduce the degree of pain, stabilize circulation parameters, and realize patients' ambulation out of bed earlier, with high safety.