The parabolic index optical fiber with uniaxial crystal cladding was studied by the vector-field method under the assumption of weakly-graded-index in the core. The power distribution in core and cladding for fundamental mode is analyzed. It is shown that the influence of parameter τ(the ratio of axial permittivity to transverse-permittivity in the cladding) to the power distribution for lower frequency is obvious,but it is negligible for higher frequency. Using the material of large τ to make the cladding is advantaged for the single-mode transmission in this kind of fiber.