Objective To observe the change of the diameter of optic nerve sheath (ONDS) in patients with common head low and foot high position during laparoscopic surgery, and evaluate the effect of non-steep Trendelenburge position on intracranial pressure. Methods Fifty-one patients scheduled for laparoscopic radical resection of rectal, prostate and bladder cancer, aged 18-80 years, with ASA gradeⅠ-Ⅲ, were divided 21 patients with a head low≤10 degree (group A) and 30 patients with a head low 10-20 degree (group B). All patients received general anesthesia and mechanical ventilation. CO2 pneumoperitoneum pressure maintained at 13 mmHg during the operation. Their optic nerve sheath diameters (ONDS), mean arterial pressure (MAP), airway plateau pressure (Pplat) and partial pressure of carbon dioxide(PaCO2) were recorded at seven predetermined time points: before anesthesia (T0), after anesthesia (T1), 5 minutes (T2), 1 hour (T3) and 2 hours(T4) after pneumoperitoneum and the trendelenburg position, before the release of the pneumoperitoneum (T5) and 5 minutes after resumption of position and deflation (T6). Results At T2-5, ONDS in both groups increased significantly (P<0.05), and continued to increase until recovered at T6. At T2-6, ONDS in group B were higher than in group A. In group B, T6 ONDS were higher than T0 (P<0.05). The results of multiple linear regression analysis showed that the tilt angle of T-position was associated with patients’optic nerve sheath diameters(B=0.058，P=0.018). Conclusion The non-steep T position has an effect on the diameter of the optic nerve sheath in patients undergoing laparoscopic surgery, and as the tilt angle increases. The nerve sheath widens more significantly and the recovery time is prolonged