Objective To retrospectively analyze the distribution and antimicrobial resistance changes of Gram-negative (G^-) bacteria, as well as related clinical characteristics of peritoneal dialysis-related peritonitis (PDRP) in elderly patients, provide reference for clinical diagnosis and treatment. Methods Elderly PDRP patients in three tertiary first-class hospitals in a city from January 2015 to December 2022 were analyzed, distribution and antimicrobial resistance of G^- bacterial PDRP pathogens, as well as incidence, clinical characteristics and prognosis of PDRP were analyzed. Results A total of 247 elderly peritoneal dialysis (PD) patients developed 406 episodes of PDRP. The overall incidence and incidence of Gram-positive (G⁺) bacterial PDRP in elderly PD patients showed a downward trend year by year (both P<0.05), while the incidence of G^- bacterial PDRP showed no significant downward trend (P>0.05). A total of 96 cases (106 episodes) of G^- bacterial PDRP occurred in elderly PD patients, with Escherichia coli being the predominant strain (38.68%). Compared with 2015-2018, there was no significant change in the susceptibility rates of G^- bacteria isolated from elderly PDRP patients to piperacillin/tazobactam, cefo- perazone/sulbactam, imipenem, meropenem, and amikacin in 2019-2022, all of which were highly susceptible. The resistance rate to cefotaxime increased (P=0.033). Multivariate logistic regression analysis showed that high serum C-reactive protein, high white blood cell count in PD fluid on the first day, and long time for white blood cell count in PD fluid to return to normal were risk factors for G^- bacterial PDRP in elderly PD patients (all P<0.05). The cure rate of elderly PDRP patients in G^- bacterial group (83.96%) was lower than that of the G⁺ bacterial group (93.01%), with statistically difference (P<0.05). Conclusion There is no obvious downward trend in the incidence of G^- bacterial PDRP in elderly PD patients, aminoglycosides can be used as the first choice for empirical treatment of G^- bacterial PDRP.