The invention relates to a novel double-redundancy electro-hydrostatic actuator (EHA) adopting a novel hydraulic cylinder based on a single-output-rod hydraulic symmetry principle. The double-redundancy EHA mainly comprises two EHA bodies, namely an upper passage EHA body and a lower passage EHA body which are exactly identical, and a novel series hydraulic cylinder, wherein each EHA body comprises a DSP (Digital Signal Processing) controller, a power drive unit, a direct-current brushless motor, a bidirectional servo pump, one-way valves, an energy accumulator, a damping bypass valve, safety valves, a current sensor, a revolution speed sensor and pressure sensors; the series hydraulic cylinder comprises four chambers, namely a chamber A, a chamber B, a chamber C and a chamber D, the action area of the chamber A is the same as that of the chamber D, the action area of the chamber B is the same as that of the chamber C, and the chambers (B and C) and the chambers (A and D) are respectively connected with an oil inlet / outlet of the upper passage EHA body and an oil inlet / outlet of the lower passage EHA body. According to the designed double-redundancy EHA, the size and weight of the existing double-redundancy EHA can be reduced, and the change to the existing EHA is minimal; the designed novel hydraulic cylinder is simple in structure, convenient to manufacture and easy to implement, and thus, the application prospect is broad.