The invention discloses a differential evadible system of an electric field for an unmanned aerial vehicle polling live wires and a method. The system comprises a polling unmanned aerial vehicle which is provided with an electric field evadible device. The device comprises a DSP (Digital Signal Processor) data processing module and two identical electric field measuring circuits. Each electric field measuring circuit comprises an electric field measuring sensor, a signal processing unit and an A/D (Analog to Digital) conversion unit which are connected sequentially. The A/D conversion unit is connected with an input of the data processing module, an output end of the DSP data processing module is connected with an airborne flight control system. The differential evadible system of the electric field for the unmanned aerial vehicle polling live wires provided by the invention can evade power transmission lines by the unmanned aerial vehicle, avoids collision of the unmanned aerial vehicle and the power transmission lines caused by error of GPS (Global Positioning System) navigation, overlarge gust when the unmanned aerial vehicle polls the live wires, or deviation of a predetermined course of the unmanned aerial vehicle which is not enough in flight altitude in the process of executing the task, the safety of a line patrol system of the unmanned aerial vehicle and the transmission lines is ensured, the reliability of line patrol operation is enhanced, and the safety of personnel, power grids and devices is guaranteed.