Objective To analyze the temporal changing trend of postoperative pneumonia (POP) monitoring data in a tertiary first-class cancer hospital in Fujian Province from 2018 to 2023, and provide reference for the effectiveness of implementation of healthcare-associated infection (HAI) prevention and control measures. Methods The temporal changing trend of POP monitoring data of cancer patients in this hospital from 2018 to 2023 was analyzed by Joinpoint regression model, and the average annual percentage change (AAPC) was calculated. Results From 2018 to 2023, the POP incidences of all cancer patients and patients with different tumors in this hospital were as follows: 3.46% in all cancer patients, 4.77%, 18.16%, 11.50%, 4.66%, 0.85%, 3.74%, and 0.46% in patients with lung cancer, esophageal cancer, gastric cancer, intestinal cancer, gynecological tumors, hepatobiliary-pancreatic tumor, as well as head and neck tumors, respectively. From 2018 to 2023, the POP incidence of all can-cer patients in the hospital decreased from 5.47% to 1.73%, and POP incidences of patients with lung cancer, gastric cancer, and intestinal cancer decreased from 12.23%, 14.93%, and 4.40% to 2.60%, 3.73%, and 2.09%, respectively. Joinpoint regression model analysis showed that from 2018 to 2023, the AAPC of POP incidence of all cancer patients in the hospital was -19.78%, and the AAPCs of patients with lung cancer, gastric cancer, and intestinal cancer were -23.69%, -27.30%, and -19.40%, respectively. The incidences of POP in all cancer patients, as well as patients with lung cancer, gastric cancer, and intestinal cancer all showed downward trends, and the differences were all statistically significant (all P<0.05). According to age, the AAPCs of the ≤60 and >60 year old groups were -22.02% and -20.48%, respectively, both groups showed statistically significant difference in trends (both P<0.05). In terms of gender, the AAPCs of the male and female groups were -16.56% and -28.35%, respectively, both groups showed statistically significant difference in trends (both P<0.05). From 2018 to 2023, Klebsiella pneumoniae showed a significant upward trend in the constituent of POP pathogens in cancer patients, with an AAPC of 6.92%, and the difference was statistically significant (P<0.05). Conclusion The incidences of POP in some cancer patients in the hospital present significant downward trends, indicating that HAI infection prevention and control measures are effective, but it is still necessary to strengthen the meticulous management of the whole perioperative process.