Objective To investigate the influence of bronchoalveolar lavage (BAL) combined with mechanical ventilation on short－term clinical effect,pathogenic bacteria conversion rate and laboratory index of patients with lung cancer and infection after operation. Methods From October 2014 to October 2017,110 patients with lung cancer and infection after operation in the First People＇s Hospital of Pinghu were chosen and randomly divided into two groups,with 55 patients in each group. The control group received mechanical ventilation,and the observation group received BAL combined with mechanical ventilation. The short － term clinical effect, pathogen clearance rate, the levels of respiratory mechanics index and inflammatory cytokines before and after treatment of the two groups were compared. Results The short－term effective rates of the control group and the observation group were 72. 73% , 94. 54% ,respectively. The pathogen clearance rates of the control group and the observation group were 72. 73% , 96. 36% ,respectively. The short － term effective rate and pathogen clearance rate of the observation group were significantly higher than those of the control group(χ2=9. 87,10. 07,all P＜0. 05). The levels of Raw,PIP and Cydn of the observation group after treatment were ( 8. 15 ± 1. 33 ) cmH2O, ( 14. 15 ± 2. 29 ) cmH2O, ( 33. 27 ± 8. 09)cmH2O,respectively, which were significantly better than before treatment and those of the control group [(12.26±1.87)cmH2O,(22.36 ±3.14)cmH2O,(25.96 ±6.95)cmH2O](t=4.98,6.44,4.67,3.19,3.56, 3. 30,all P＜0. 05). The levels of hs－CRP,TNF－α,IL－8 and PCT of the observation group after treatment were (48. 43 ± 11. 20)mg/L,(11. 05 ± 2. 42) ng/L,(96. 72 ± 12. 09) ng/L,(14. 26 ± 2. 33) ng/L,respectively,which were significantly better than before treatment and those of the control group[(63. 01 ± 15. 42)mg/L,(24. 12 ± 4.75)ng/L,(142.54 ±20.40)ng/L,(20.77 ±4.15)ng/L](t=3.89,3.44,4.16,4.95,2.67,2.51,3.17,3.46, all P ＜0. 05). Conclusion BAL combined with mechanical ventilation in the treatment of patients with lung cancer and infection after operation can efficiently control the respiratory symptoms,accelerate the removal process of pathogenic bacteria, improve the respiratory mechanics and is helpful to reduce the levels of inflammatory cytokines.