A novel fiber model with isotropic crystal cladding, uniaxial anisotropic crystal fiber core that optical axis is parallel to the x-axis is proposed. The field intensity distribution is approximately obtained by waveguide equation. Using the transmission matrix method and numerical simulation method, the dispersion curves that the propagation constants β of o ray and e ray change with normalized frequency V are analyzed. By deeply analyzing the influence made by cores of optical fibers on dispersion curves, it is shown that the radii of optical fiber cores don′t exert influence on cutoff frequency. Based on the above results, the curves that the propagation constants β of o ray and e ray change with optical fiber core are achieved respectively. By analyzing the influence of the dielectric constants on dispersion curves, it is indicated that the polarized direction of light in the fiber can be changed by the ratio of x directional dielectric constant and y directional dielectric constant in the certain range of normalized frequency propagating in the fiber. This work provides a theoretical foundation for designing the polarization fiber.