Objective To investigate the effect of individualized PEEP titration on the distribution of lung ventilation by thoracic impedance tomography (EIT). Methods A total of 70 patients, aged 18-65 years, BMI 18−28 kg/m2, ASA classification grade I-II, operation time≥2h, who underwent elective laparoscopic gynecological surgery were selected. They were randomly divided into two groups (n=35): low tidal volume group (group PV: VT = 6 ml/kg) and conventional tidal volume group (group CV: VT = 10 ml/kg). Tidal volume in the two groups was set according to ideal body weight (PBW). Except for the standard monitoring, all patients used thoracic impedance tomography to monitor center of ventilation (COV). Individual PEEP titration was performed at three time points after endotracheal intubation, establishment of pneumoperitoneum Trendelenburg position and evacuation of pneumoperitoneum Trendelenburg position. The whole titration process was guided with EIT. Observe and record COV, HR, MAP before intubation (T0), immediately after intubation (T1), after three titrations (T2, T3, T4) and 30min after extubation (T5). Platform pressure (Plat), drive pressure (DP) of T1-T4 and individual PEEP of the three titrations were recorded. Record PH, arterial blood oxygen partial pressure (PaO2), arterial blood carbon dioxide partial pressure (PaCO2) of T0, T1, T4, T5. The fluid volume, the use of vasoactive drugs, operation time and the incidence of postoperative pulmonary complications were recorded. Results 1.Compared with group CV, the COV of T1-T4 was increased in group PV (P 0.05). Compared with T0, the COV in both groups was decreased at T1-T5 (P 0.05); Compared with T5, the COV in both groups was decreased at T1-T4(P 0.05). 2.Compared with group CV, individualized PEEP in group PV was increased (P 0.05), but the Plat and DP in group PV was decreased (P 0.05). Compared with T3, individualized PEEP in both groups showed decrease at T2 and T4 (P 0.001), while the Plat and DP showed decrease at T1, T2, and T4 (P 0.001); the Plat and DP increased at T2-T4 compared with T1 (P 0.001). 3. HR showed decrease at T0-T4 compared with T5 (P 0.001). Compared with T0, MAP at T1-T4 was decreased (P 0.001), while the PaO2 and OI showed increase at T1 and T4 (P 0.001). There were no significant differences in the other indicators (P0.05). Conclusion 1.Low tidal volume combined with individualized PEEP ventilation can reduce ventral displacement during mechanical ventilation, improve ventilation distribution, and reduce driving pressure and plateau pressure in gynecological laparoscopic patients, but have no effect on postoperative pulmonary complications. 2.Low tidal volume ventilation requires greater PEEP than conventional tidal volume.