The symmetrical design of the aircraft's wings and control surfaces determines the system framework in which the sensors， computers， and actuators of the flight control system are stributed and symmetrically installed on the aircraft， and the even number n-redundant architectural design is adopted. In the practical engineering， the balanced division of labor in the productive relations of redundant parts and the differences in design and manufacturing between different manufacturers would inevitably appear the case of two singular faults such as：‘ two-party opposition' even separation uncertain fault and‘ mutual disapproval’. The criterion of‘ variation memory， redundancy reconstruction and high probability failure of extreme signals’ for singular faults is proposed. In an even redundancy system， the sample median is calculated based on the signal variation at the endpoint of the median interval. The fault criterion is based on the variation consistency between signal and the participating voting signals. The four signals are reconstructed into the‘ second largest， second smallest and reference signal’， which is a reconstructed triple redundancy. The two signals are reconstructed into‘ original two signals + reference signal’， which is a reconstructed triple redundancy as well. The redundancy econstruction criterion is formed by the four signals reconstruction and two signals reconstruction. The study in this paper provide an effective voting monitoring solution for the four-redundant signal‘ 2∶2 uncertain fault， 1∶1∶1∶1 multiple fault’ and the two-redundant signal 1∶1 fault for fault criterion and the redundancy reconstruction criterion. In the case of three-redundant signal 1∶1∶1 multiple fault， according to the following quality between the signal and the median signal， the non-median signal close to the median is normal， and the non-median signal far from the median is faulty.