Objective To explore the difference between metagenomic next⁃generation sequencing（mNGS） and traditional culture etiological diagnosis in patients with severe pneumonia in bronchoalveolar lavage fluid （BALF）and the impact of mNGS results on the adjustment of antibiotic strategy. Methods A retrospective analysis was performed on the patients with severe pneumonia who had received both traditional BALF culture and mNGS during hospitalization in the department of critical care medicine of the Affiliated Hospital of Guizhou Medical University from August 2019 to April 2021. The differences between mNGS and culture findings were compared，and the positive rate，consistency and antibiotic regimen adjustment were analyzed. Results A total of 75 patients were enrolled. The positive rate was 97.3% for mNGS and 41.3% for traditional culture. The positive rate of bacterial detec⁃ tion was 94.7% for mNGS and 38.7% for traditional culture. The most common detectable fungus was Pneumocystis jirovecii（24.0%）in mNGS. The positive rate of rare bacteria，atypical bacteria，fungi and viruses was much higher in mNGS than in traditional culture. The consistency of etiological detection results between the two groups was poor （Kappa = 0.038，P = 0.229），and more types of microorganisms were detectable by mNGS than by traditional culture. Based on mNGS test results，antibiotic regimens were adjusted in 69% of the patients. Conclusions mNGS has a higher sensitivity in the etiological detection in patients with severe pneumonia，especially for those with immu⁃ nosuppression. And mNGS is helpful for clinicians to adjust antibiotic strategies for patients with severe pneumonia.