The effects of a polarization field on the current transport mechanisms in ultraviolet light emitting diodes (UVLEDs) are studied by analyzing forward current-voltage (Ⅰ Ⅴ) characteristics based on the experimental data and theoretical simulation.The results indicate that polarization electric field suppresses the diffusion current and meanwhile enhances the tunneling current in the metal-face UV LEDs under forward bias.The presence of a large polarization field in the deep UV-LEDs is responsible for the current transport mechanism dominated by the tunneling process at a moderate forward bias.