Abstract: Under icing conditions in multi-branch short-distance distribution network transmission lines, the application of DC de-icing technology faces limitations, while the conventional power-frequency AC short-circuit de-icing method presents challenges such as low power factor and discontinuous voltage regulation. This paper proposes an efficient low-frequency variable-frequency de-icing method for distribution networks. Through numerical analysis of circuit models, the principle of frequency-conversion de-icing is systematically investigated. Considering the magnetic saturation characteristics of distribution transformer cores, we developed an optimal de-icing frequency calculation method based on non-disconnection on the primary side of distribution transformers; meanwhile, we designed a novel 0.5 MVA lightweight frequency-conversion de-icing device with 3×3 matrix converter topology, which is capable of generating AC de-icing voltage outputs ranging from 0~694 V at 1~80 Hz with maximum current of 840 A, meeting the de-icing requirements for distribution networks within 0~5 km. Experimental verification conducted in Chongqing University's artificial climate chamber demonstrates that, when the frequency is reduced from 50 Hz to 40 Hz under equivalent voltage, the de-icing time for 300 mm², 150 mm², and 95 mm² cross-section conductors is reduced to 0.58, 0.65, and 0.73 times the original duration, respectively. This research provides theoretical foundations and practical references for distribution network de-icing.