Objective: To investigate the influences of different pressures of CO2 pneumoperitioneum on liver function, arterial blood gas, and neck or shoulder pain following laparoscopic cholecystectomy (LC). Methods: One hundred and twenty patients scheduled for elective LC were randomly assigned to group A, B and C, with 40 cases in each group. The CO2 pneumoperitoneum pressure was maintained at 10 mmHg in group A, 12 mmHg in group B and 14 mmHg in the group C. The liver function and blood gas parameters before and after operation, and the incidences of nausea, vomiting, and neck or shoulder pain on the first to third postoperative day of the three groups were compared and analyzed. Results: The preoperative data among the three groups had no statistical differences (all P>0.05), but the parameters of liver function and arterial blood gas as well as the incidence of nausea, vomiting, and neck or shoulder pain after operation were all significantly different among them (all P<0.05). The results showed that the higher the pneumoperitioneum pressure was increased, the more significantly did the parameters of liver function (increase of AST, ALT and TBIL) and arterial blood gas (increases of PO2, and decrease of pH and PCO2 ) change, and the higher was the incidence of nausea, vomiting, and neck or shoulder pain. Conclusion: The CO2 pneumoperitioneum pressure has significant impact on incidence of liver function abnormalities, arterial blood gas derangements, and neck or shoulder pain following LC. Therefore, the pneumoperitioneum pressure should be decreased as low as possible during operation.