Abstract: OBJECTIVE To explore the risk factors for pulmonary infection in elderly hospitalized patients with Alzheimer’s disease（AD） and early warning value of blood procalcitonin（PCT）. METHODS A total of 158 elderly patients with AD who were hospitalized in the Third Hospital of Quzhou from Oct 2018 to Jan 2020 were enrolled in the study, the risk factors for the pulmonary infection in the elderly hospitalized patients were screened out, and the value of the PCT in early warning of pulmonary infection was evaluated. RESULTS The incidence rate of pulmonary infection was 27.85% among the elderly AD patients. Among the pathogens causing the infection, the gram-negative bacteria accounted for 65.91%, 27.27% of which were Pseudomonas aeruginosa, and 22.73% were Escherichia coli. The gram-positive bacteria accounted for 34.09%, 18.18% of which were Staphylococcus aureus. Univariate analysis showed that the incidence of pulmonary infection was high among the elderly AD patients complicated with diabetes mellitus, long bed ridden time, complication with hypoalbuminemia, and difficulty eating（P＜0.05）. The PCT level of the infection group was significantly higher than that of the non-infection group, the lymphocyte counts of the infection group were significantly lower than those of the non-infection group（P＜0.05）. The diabetes mellitus, long bedridden time, hypoalbuminemia and difficulty eating were the independent risk factors for the pulmonary infection in the elderly patients with AD（P＜0.05）. The sensitivity of PCT was 81.82% in prediction of pulmonary infection, the specificity 94.74%. CONCLUSION The AD patients with diabetes mellitus, long bedridden time, hypoalbuminemia, difficulty eating and high PCT level are at higher risk of pulmonary infection, and the early warning value of the PCT is high, and it can be used for monitoring of pulmonary infection.