To further understand how the rime ice trees of different forms affect the surface electric field and the corona onset characteristics of iced conductors, using four kinds of conductors, we tested their corona onset voltages under rime-iced condition and different electric fields in an artificial climate chamber. In the tests, we used an ultraviolet imager and the curve-fitting method to study the corona onset voltages of the conductors. Moreover, using the finite element method (FEM) software, Ansoft, we modeled and calculated the electric field distribution around the rime ice-tree tips according to different rime forms. The results show that, the rime icing significantly decreases the corona onset voltage of a conductor. However, the corona onset voltage may fluctuate with various ice-tree shapes. In the same iced period, the thicker wires are affected less by the rime than the thinner ones. The increase in diameter of a conductor due to the icing will raise the corona onset voltage of the conductor at a gradually slowing speed. The icing-water conductivity does not influence the rime morphology and the corona onset voltage. The branches rime ice will increase the conductor roughness and consequently distort the electric field of the conductor. The results can be used as a reference for studying the corona onset characteristics of transmission line in the icing areas.