Space-borne integrated path differential absorption(IPDA) lidar has been regarded as an efficient method to measure the concentration of the global atmospheric CO2 column concentration all day long. As a key part of the lidar receiver, the performance of the photodetector has a significant influence in the overall lidar system. Avalanche photodiode(APD) is widely used in space-borne lidar because of its large dynamic range and high responsivity. The basic theories of the APD detector and the IPDA lidar were briefly introduced. And taking the actual working conditions of the space -borne IPDA lidar into account, the actual performances of an APD detector such as the detector′s responsivity, dynamic range, linearity and the signal to noise ratio under different optical powers were tested. Then based on the experiment result, the influence caused by the performances of the detector on concentration inversion was analyzed. The result shows that, when the CO2 concentration is 400 ppm, and the on-line wavelength output voltage of the APD detector is between 280 mV and 980 mV, the CO2 concentration error caused by the non-linearity and noise of the APD detector is less than 0.8 ppm.