The invention relates to an ice melting method for overhead contact system of an electrified railway and an ice melting system thereof. Major hazards of ice coating of the overhead contact system include accidents that pantograph of electric locomotives can not contact with a contact line to obtain current, contact system brandishes, even falls of piles and collapses, and the like. In the ice melting method and the ice melting system thereof, an upper overhead contact system and a lower overhead contact system are connected in series to form a circuit by a section post, AC or DC ice melting current is input at the head end of the circuit, ice coating thickness and safe ice melting current value are obtained by analyzing meteorological and overhead contact system parameters with an ice coating data processing and control module, and then the ice melting system is controlled to output the ice melting current at the end of the circuit, thus ice is molten by Joule heat generated by the current. In the ice melting method and the ice melting system thereof, ice attached to the contact line is molten by joule heat, and compared with the deicing modes of artificial knock and the like of operation departments, the ice melting method and the ice melting system thereof greatly improve deicing efficiency, thus reducing the effect on railway transport, and eliminating damages of external force on the contact line.