Influences of Lorentz shape instead of Voigt shape on airborne CO2 column ratio precision measurement in integrated path differential absorption (IPDA) lidar are studied in this paper. The differences of temperature and pressure sensitivity, and relative random error between two line shapes with the platform height are investigated by model simulation. The result shows that, there are small differences between two line shapes in the bottom atmosphere for absorption cross-section, temperature and pressure sensitivity, and relative random error, which are 0.860%, -0.703% and 0.224% respectively, while the time of computation of spectral parameters can be effectively reduced by using Lorentz shape. The airborne IPDA lidar using Lorentz shape can provide rapid and efficiency ability to retrieve CO2 column ratio along the flight track, lower requirement of system computational capability, retrieve and analyze data during flight and manage flight strategy on the emergency. Meanwhile it will further contribute to realize the miniaturization and integration of airborne lidar system.