The influences of atmospheric temperature, humidity and pressure uncertainties on space-borne integrated path differential absorption (IPDA) lidar measuring atmospheric column-averaged CO2 concentrations are studied. The column-averaged CO2 concentrations measurement principle and CO2 absorption cross section calculation method are presented. The influences of atmospheric temperature, humidity and pressure errors on retrieving CO2 concentrations around on-line CO2 absorption line are analyzed and simulations are implemented. For optimal IPDA lidar on-line and off-line wave number of 6361.2250 cm-1 and 6360.99 cm-1, the total column-averaged CO2 concentration measurement error is calculated to be 0.296×10-6 with temperature error of 1 K, humidity error of 10% and relative pressure error of 0.001. The result is important for retrieval of column-averaged CO2 concentration with high precision and lidar system parameters optimization.