Solar absorption spectra collected with a high-resolution Fourier transform spectrometer is able to measure the column abundance of CO2 accurately. In the paper, the influence of a model parameters in the forward model on the retrieval of CO2 is analyzed, also the impact of a model parameters on retrieval results under different solar zenith angle and the reasons are discussed. Four model parameters, such as continuum tilt value, internal field of view, zero-level offset and Doppler shift are modified in the forward model and how the results change with the disturbance is studied, based on the spectra collected in two typical days. The results show that, the relative deviations of column-averaged dry air mole fraction of CO2(XCO2) caused by the disturbance of different a model parameters are different. Also, the relative deviations due to the disturbance of the same parameters corresponding to different time for collecting spectra are different. Continuum tilt value has the biggest influence on the retrieval, and the change of this value resulted in the relative deviations of XCO2 between 01%~02%. The changes of other three parameters internal field of view, zero-level offset and Doppler shift have small impact on the retrieval, which leads to the relative deviations of XCO2 in the range of -0045%~-002%, -0045%~0015% and -003%~004%, respectively. Finally, the reasons of the deviations are explained based on the average kernels of CO2. The results provide a basis for how to set the parameters in the retrieval algorithms and improve the measurement accuracy of atmospheric CO2.