CdTe thin film solar cells with a doped-graphite paste back contact layer were studied using admittance spectroscopy technology.The positions and the capture cross sections of energy level in the forbidden band were calculated,which are the important parameters to affect solar cell performance.The results showed that there were three defects in the CdTe thin films solar cells with the doped-graphite paste back contact layer,whose positions in the forbidden band were close to 0.34,0.46 and 0.51 eV,respectively above the valence band,and capture cross sections were 2.23×10-16,2.41×10-14,4.38×10-13 cm2,respectively. CdTe thin film solar cells with a doped-graphite paste back contact layer were studied using admittance spectroscopy technology. Positions and the capture cross sections of energy level in the forbidden band were calculated, which are the important parameters to affect solar cell performance. results showed that there were three defects in the CdTe thin films solar cells with the doped-graphite paste back contact layer, whose positions in the forbidden band were close to 0.34, 0.46 and 0.51 eV, respectively above the valence band, and capture cross sections were 2.23 × 10-16, 2.41 × 10-14, 4.38 × 10-13 cm2, respectively.