Objective To observe the clinical efficacy of compound Wufengcao liquid combined with negative pressure wound therapy with instillation (NPWTi) for the treatment of stage Ⅲ-Ⅳ pressure injury (PI), and to preliminarily explore its action mechanism. Methods (1) Clinical research: from January 2019 to October 2022, 60 PI patients who were admitted to the Scrofula Department and Wound Care Clinic at Nanjing Municipal Hospital of Traditional Chinese and Western Medicine were randomly divided into normal saline NPWTi group and compound Wufengcao liquid NPWTi group, with 30 cases in each group. Both groups underwent NPWTi under the premise of systemic basic treatment, before treatment, after removing the negative pressure device in the 1st, 2nd and 3rd weeks of treatment, the pressure ulcer scale for healing (PUSH) score, the wound bacterial culture detection rate and the wound healing time were counted, and the vascular endothelial growth factor (VEGF) content of wound tissue was detected by ELISA method. (2) Animal experiments: 24 SD rats were randomly divided into blank group, model group, normal saline NPWTi group and compound Wufengcao liquid NPWTi group, 6 rats in each group. PI rat model was established by local tissue ischemia/reperfusion injury method, and the negative pressure device was removed at the end of each day of treatment. Before treatment and 3, 7 and 10 days after treatment, the wound morphology of each group of rats was observed, the wound histopathology was observed by HE staining, the CD34 positive cells rate of wound tissue was detected by immunohistochemistry, and the expressions of p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor-κB p65 (NF-κB p65), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), arginase-1 (Arg-1) and transforming growth factor-β (TGF-β) in rat blood and wound tissue were detected by ELISA and RT-qPCR. Results (1) Clinical research: Both groups could effectively reduce the PUSH score and the wound bacterial culture detection rate, shorten the wound healing time, and promote the expression of VEGF in wound tissue, the compound Wufengcao liquid NPWTi group was better than the normal saline NPWTi group (P<0.05). (2) Animal experiments: Compared with blank group, the rats in the model group showed obvious wound inflammatory response and tissue damage, and the CD34 positive cells rate, blood and wound tissue p38 MAPK, NF-κB p65, iNOS and TNF-α levels were significantly increased, Arg-1 and TGF-β level was significantly reduced (P<0.05); Compared with model group, after 7 days of treatment, the normal saline NPWTi group and the compound Wufengcao liquid NPWTi group significantly decreased the wound morphology score, the histopathological morphology was significantly improved, the CD34 positive cells rate was significantly increased (P<0.05), the levels of blood and wound tissue p38 MAPK, NF-κB p65, iNOS, and TNF-α were significantly reduced, and the levels of Arg-1 and TGF-β were significantly increased (P<0.05), and the compound Wufengcao liquid NPWTi group was better than that of the normal saline NPWTi group (P<0.05). Conclusion Compound Wufengcao liquid combined with NPWTi can effectively promote the healing of PI wounds, and its mechanism of action may be by inhibiting the activation and expression of p38 MAPK/NF-κB signaling pathway, thereby regulating the polarization balance of M1/M2 macrophages.