In this paper, the performance of a novel design of passive polarization rotator (PR) based on silica photonic crystal fiber is studied and analyzed using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The proposed design has a rectangular core region with a slanted sidewall. The influence of the different structure geometrical parameters and operating wavelengths on the PR performance is investigated. At a wavelength of 1.55 μm, nearly 100% polarization conversion ratio is obtained, with a device length of 2839 μm. In addition, it is expected that over the 1.5 to 1.6-μm wavelength range, polarization conversion would be more than 99%.