Objective To study the effect of early mechanical ventilation in treatment of patients with severe acute pancreatitis(SAP).Methods Fifty-two patients with SAP admitted in the First People's Hospital of Zhaoqing from January 2010 to January 2015 were randomly allocated into two groups (n =26),early mechanical ventilation group(observation group) and conventional mechanical ventilation group(control group).Patients in the observation group treated with early lung protective ventilation when PaO2 ＜ 13.3kPa.Patients in the control group treated without mechanical ventilation untill PaO2 ＜ 8kPa.The symptoms,the extent of inflammatory reaction,the severity of lung lesions and the mortality of two groups were compared through monitoring vital signs,abdominal circumference,APACHE Ⅱ score,bladder pressure,oxygenation index (PaO2/FiO2),C reactive protein (CRP),procalcitonin (PCT),hospital stay and mortality.Results No statistically significant differences in the APACHE Ⅱ score,bladder pressure,oxygenation index,CRP and PCT in two groups before treatment were observed(P ＞ 0.05).The APACHE Ⅱ score (12.8 ± 7.6) points,bladder pressure (14.9± 7.9) cmH2O,CRP (48.8 ± 30.1) rmg/L,PCT (1.25 ± 0.55) μg/L,mortality (3.84％) of the observation group after treatment were significantly lower than those of the control group (t =2.057,2.091,3.252,2.697,x2 =4.305,all P ＜ 0.05),while the oxygenation index in the observation group [(300.0 ± 34.9) mmHg] was significantly higher than that in the control group [(278.1 ± 32.8) mmHg],the difference of the two groups was statistically significant (t =3.322,P ＜ 0.05).Conclusion Early lung protective ventilation is safe and effective for treatment of the patients with SAP.