In order to know the absorption characteristics of the orbit-control thruster plume, the solar infrared radiation absorbed by the plume was studied. In body-fitted coordinate, the model of the solar radiation absorbed by the plume was founded by using the finite volume method. At the plume boundary, the spectral luminance of the solar radiation which had been absorbed by the plume is obtained by calculating the model. The spectral luminance of the solar radiation absorbed is compared to the spectral luminance without absorption. The result indicates that when the distance between the plume and the nozzle exit is 0.483 m, the plume absorptance equals to one approximately at the wavenumber of 1700 cm, 2155 cm, 2175 cm, 2375 cm, 3700 cm and 3750 cm. The result is very useful to know the absorption characteristics of the orbit-control thruster plume comprehensively.