Abstract: A plutonium multi-channel γ-ray spectrum at 92 to 112 keV contains 8 γ-ray lines and 29 X-ray lines which are decayed from ²³⁸Pu,²³⁹Pu,²⁴⁰Pu,²⁴¹Pu and ²⁴¹Am. CMGA can provide isotopes abundances of a sample by analyzing its spectrum in this region. After unfolding γ-ray spectra of two samples (each sample has been measured 6 times), the value of ²⁴⁰Pu/²³⁹Pu given by CMGA2.0 normalized to that measured with mass spectrum method is 1.010±0.008 for sample 1 and 0.995±0.011 for sample 2, respectively. Precision of the results was comparatable with that from MGA and FRAM. Comparing the different fitting results from CMGA2.0 with different methods for describing the background shape, it is found that bilinear step background method can accurately describe the background shape in the multi-peak region.