Objective To explore the diagnosis efficacy of neutrophils ratio in bronchoalveolar lavage fluid combined with gram stainingforand pneumonia. Methods A total of 188 patients who received alveolar lavage fluid examination in the Department of Respiratory Medicine of Guangdong Provincial People′s Hospital from September 2018 to May 2021 were retrospectively enrolled，including pneumonia patients as the case group and non⁃pneumonia patients as the control group. Demographic data，clinical diagnosis，neutrophils ratio in bronchoalveolar lavage fluid （BALF），gram stain results and other clinical information of patients were collected，the differences between the two groups were compared，and Receiver Operating Characteristic curves （Receiver Operating Characteristic， ROC）to evaluate the neutrophils ratio in BALF and the diagnostic value of Gram stain in patients with pneumonia. Results There were 108 cases in pneumonia group and 80 controls in non⁃pneumonia group. In cases group， patients with Community ⁃ acquired pneumonia were 74，patients withHospital ⁃ acquired pneumonia were 34. The bronchoalveolar lavage fluid neutrophil ratios of patients with pneumonia were significantly higher than those of patients without pneumonia（P < 0.01）. On the diagnosis of pneumonia，the value of cut⁃off，sensitivity，specificity and the area under ROC curve of neutrophil ratio in bronchoalveolar lavage fluid（BALF）for diagnosis of pneumonia were respectively 41.45，0.750，0.675 and 0.728. The Cut ⁃off of neutrophil ratio in BALF combined microscopic gram staining for the diagnosis of pneumonia was 22.09%，with a sensitivity of 0.724，specificity of 0.703，and an area under ROC curve was 0.731. The diagnosis effect of neutrophil ratio in BALF combined gram stain was higherthan only neutrophil ratio in BALF. The more higher neutrophils ratio in BALF，the higher sensitivity in patientswith pneumonia. Conclusion BALF neutrophils ratio combined with gram stain is significantly on the diagnosis ofpneumonia.