Abstract:  By measuring the polarization information of insects in the beam, entomological radar can estimate the orientation of insect, and then complete the trajectory monitoring of migratory insects. However, some non-ideal factors in the fully polarimetric radar system will affect the accuracy of insect orientation estimation. In order to study the influence of amplitude and phase imbalance between channels in fully polarimetric radar system on orientation measurement, the polarization scattering characteristics of insect and fully polarimetric system are modeled, the orientation error is analyzed, and the relationship between orientation error and channel imbalance is obtained. Theoretical analysis and simulation results show that the insect orientation error is related to the system, its own scattering characteristics and the real orientation, and the channel imbalance will cause the estimated insect orientation to deviate to the polarization direction. These works provide a new way for the design of fully polarimetric radar.