Polarization properties of the leaky coaxial cables (LCXs) have significant effects on the fluctuation of the received signal. Therefore, the knowledge of the polarization state of LCXs is helpful to design LCXs with uniform radio wave coverage. In this paper, the physical understanding of the radiation from LCXs is presented first, and then a hybrid method involving finite difference time domain method and integration of equivalent electrical and magnetic currents is used to simulate and analyze the polarization properties of LCXs with circumferentially asymmetry slot. It is found that the LCXs with circumferentially asymmetry slots can excite both the circumferential and axial components of the field, and the magnitude and phase differences between them significantly depends on the structural parameters of the slot. Therefore, it is possible to design LCX with desired polarization property by properly choosing the structural parameters.