Objective To investigate the effects of different antibiotics on gut microecology in patients with pneumonia.Methods A total of 300 patients with pneumonia admitted to Jilin City People's Hospital from July 2020 to September 2021 were selected as the research objects.They were divided into control group,Cefuroxime Sodium group,Levofloxacin group,Cefoperazone group and Imipenem group by random number table method,with 60 cases in each group.Intestinal microbiota culture combined with matrix-assisted laser desorption ionization time-of-flight mass spectrometry was used to detect intestinal microbiota in all patients.The intestinal flora of the control group was detected before antibiotic administration,and the intestinal flora of the other four groups was detected 7 d after antibiotic administration.The changes of the total amount and proportion of intestinal bacteria,fungi and probiotics and the diversity of intestinal flora were compared among the five groups.Results The total number of bacteria and probiotics in control group,Imipenem group,Cefoperazone group,Levofloxacin group and Cefuroxime Sodium group decreased successively,and the differences were statistically significant(P ＜0.05).The Cocci/Bacilli of Cefoperazone group and Imipenem group were higher than those of control group and Levofloxacin group,and the differences were statistically significant (P＜0.05).The number of fungi in Cefoperazone group and Imipenem group were higher than those in control group,Cefuroxime Sodium group and Levofloxacin group,and the differences were statistically significant (P＜0.05).The number of bacteria genera and species in Imipenem group and Cefoperazone group were lower than those in control group,Cefuroxime Sodium group and Levofloxacin group,and the differences were statistically significant (P ＜0.05).Conclusion The higher the level of antibiotics used,the wider the antibacterial spectrum,the less the species and number of gut microbiota,the more the number of fungi,the more serious the imbalance of gut microbiota.