Objective To evaluate the impact of the trusteeship of Guang’an People’s Hospital by West China Hospital, Sichuan University on its operational efficiency and quality, so as to provide empirical evidence for the construction of trusteeship-style medical alliances. Methods Annual operational data of Guang’an People’s Hospital from 2013 to 2024 were collected. Taking the initiation of trusteeship in September 2015 as the intervention point (2013-2015 as the pre-trusteeship period and 2016-2024 as the post-trusteeship period), 15 evaluation indicators were selected across six dimensions: operational efficiency, economic performance, medical service quality, discipline development and research, workforce development, and patient satisfaction. Between-group comparisons were performed using the Welch t-test or Mann-Whitney U test. Interrupted time series analysis (ITSA) with segmented regression was conducted to assess level and trend changes of each indicator before and after the trusteeship, with the Newey-West method used to correct for autocorrelation and the Durbin-Watson statistic to test residual autocorrelation. Results Compared with the pre-trusteeship period, annual outpatient and emergency visits, annual discharges, total revenue, medical revenue, the proportion of level-Ⅲ and level-Ⅳ surgeries, total research funding, and the number of locally trained postgraduate staff increased significantly after trusteeship (P<0.05), while the drug revenue proportion and bed occupancy rate decreased significantly (P<0.05). ITSA results showed that after trusteeship, the growth trend of annual outpatient and emergency visits was significantly enhanced (β3=35941.23 visits/year, P<0.05); the average length of stay declined at an accelerated rate (β3=?0.17 days/year, P<0.05); the bed occupancy rate fell significantly (β3=?8.20 percentage points/year, P<0.05); the decline in drug revenue proportion further accelerated (β3=?1.05 percentage points/year, P<0.05), dropping from 41.8% to 19.6%; the growth trend of examination revenue proportion increased significantly (β3=0.61 percentage points/year, P<0.05); the proportion of level-Ⅲ and level-Ⅳ surgeries rose instantly by 6.89% (P<0.05); and the growth slope of locally trained postgraduate staff increased significantly (β3=7.97 persons/year, P<0.05). No statistically significant level or trend changes were observed for annual discharges, total revenue, or medical revenue (P>0.05); the number of research projects, total research funding, and publications showed no sustained improvement after trusteeship (all β3<0, P<0.05); and outpatient and inpatient satisfaction scores stayed high and stable at approximately 95 points. Conclusions The trusteeship-style medical alliance model of West China Hospital, Sichuan University has effectively and significantly strengthened the long-term growth trend of service volume in the trustee hospital, continuously improved its operational efficiency and revenue structure, markedly enhanced its capacity for the diagnosis and treatment of complex and severe diseases, and effectively promoted the development of local healthcare personnel. This model provides a replicable practical pathway for deepening the reform of the medical and health system and promoting the downward extension of high-quality medical resources.