The invention relates to an inductive power taking device of a power transmission line, and a maximal power obtaining method of the device, and belongs to the technical field of inductive power takingof the power transmission line. The device is composed of a storage battery charging module, a load power supply module and a protection module. The method comprises that the maximal power obtained by the inductive power taking device of the power transmission line serves as an objective function, and a target value of load change is calculated; and the inductive power taking device charges an energy-storing storage battery, power is supplied to load terminal equipment continuously and stably, and the maximal power output by the device is obtained according to relation between output power when the load is not purely resistive and output power when the load is purely resistive. Thus, the inductive power taking efficiency can be improved, long-term stable power supply guarantee is providedfor line equipment, and safe operation of the power transmission line is ensured.