In order to research the effects of the concentration of the scattered medium on the polarization degree of the scattered light in near-infrared detection and the relation of the polarization degree of the target and the ratio of the impurity, the numerical results of the Müller matrix and the polarization degree were calculated. The results showed that the concentration of the scattered medium has significant effect on the depolarization degree of the scattered light. And then the numerical relation between the polarization degree of the target and the ratio of the impurity were discussed by building the mixed target model. The normalized polarization degree was obtained in addition. The inversion result of the ratio of the impurity can be obtained from the normalized polarization degree. The result can be applied as a new approach of the atmosphere remote sensing.