Objective To investigate the relationship between serum level of pyruvate kinase M2(PKM2),galec-tin-3(Gal-3)and citrolinated histone H3(CitH3)and pulmonary infection in patients with mechanical ventilation(MV).Methods A total of 120 patients with MV admitted to Jinhua Central Hospital from October 2022 to March 2024 were included in the study.They were divided into pulmonary infection group(n=50)and non-pulmonary in-fection group(n=70).Serum level of PKM2,Gal-3 and CitH3 was detected by ELISA.The patients were divided into good prognosis group(n=79)and bad prognosis group(n=41).Multivariate Logistic regression analysis was performed to analyze the factors affecting the adverse prognosis of MV patients.Receiver operating characteristic(ROC)curve was used to analyze the predictive value of serum PKM2,Gal-3 and CitH3 for poor prognosis in pa-tients undergoing MV.Results Compared with non-pulmonary infection group,serum level of PKM2,Gal-3 and CitH3 in pulmonary infection group was increased(P<0.05).The level of serum PKM2,Gal-3 and CitH3 in the poor prognosis group was increased(P<0.05).The Clinical Pulmonary Infection score(CPIS)of the poor progno-sis group was higher than that of the good prognosis group(P<0.05).PKM2,Gal-3 and CitH3 were all risk factors for poor prognosis in MV patients(P<0.05).The area under the curve(AUC)of PKM2,Gal-3,CitH3 and com-bined prediction of poor prognosis were 0.712,0.839,0.779 and 0.925,respectively.AUC of combined diagnosis of PKM2,GAL-3,CITH3 and combined diagnosis was better than that of single detection(Z=4.261,2.521,3.676,P<0.001,0.05,0.001).Conclusions The serum level of PKM2,Gal-3,and CitH3 in MV patients with concurrent pulmonary infections is found to be higher than those in those without pulmonary infections,so these three factors have potential predictive value for poor prognosis of MV patients.