Objective To evaluate the effect of lung compliance and intrapulmonary shunt by increasing the inspiratory time during one lung ventilation(OLV). Methods Forty-six age 20-65 years of age, ASA ⅠorⅡgrade patients, scheduled for selective thoracoscopic lobectomyunder lateral decubitus position were randomy divided into two groups with 23 each:C and E groups. After one lung ventilation,the inspiratory-to-expiratory ratio was adjusted during mechanical ventilation.Arterial blood gas analysis and respiratory parameters was determined after two lung ventilation (TLV) 15min(t0) and 30min(t1), 60min(t2) after OLV. Intrapulmonary shunt (Qs/Qt) and lung compliance(Cdyn) were calculated. Results Two groups Peak airway pressure (Ppeak), airway plateaupressure(Pplat) and Qs/Qt increased in t1 and t2 when compared with t0(P<0.001). PaO2, SaO2 and Cdyn decreased(P<0.001). Ppeak, Pplat(P<0.001) and Qs/Qt (P=0.021) decreased obviously in t1 and t2 in group E when compared with group C. Group E had a better PaO2(P=0.034), SaO2(P=0.03) and Cdyn(P<0.001) in t1 and t2. The difference was all statistically significant. Conclusion In the lateral position, using I:E=1:1 compared with I:E=1:2, it is advantageous to reduce the Ppeak, Pplat and Qs/Qt, improve the dynamic compliance of the lung.To a certain extent, it's improving arterial oxygenation.