A novel polarization rotator (PR) is proposed based on a spiral photonic crystal fiber aided by liquid crystal. The proposed PR has an ultrashort length of only ∼4.17 μm and a low cross talk of ∼-20.93 dB, and the proposed PR offers a nearly 100% polarization conversion efficiency for the whole C-band. In addition, a large temperature tolerance of ∼±5°C and a large rotation angle tolerance of ∼±4° can be accepted based on the full-vector finite-element method simulation. The proposed PR is a potentially effective polarization conversion device for applications in modern communication systems.