The invention belongs to the technical fields of industrial control system safety protection and other technical fields with high requirements for system safety and reliability, and particularly relates to an output decision device and method for a heterogeneous triplication redundancy processor. The device comprises three heterogeneous processors for providing service for the external, a synchronizer, an output decision device and a washer. The heterogeneous processors are connected with the synchronizer, the output decision device and the washer. Since the output decision device can change the decision strategy and its mode according to the external configuration parameter, on one hand, the probability of outputting the wrong result of the heterogeneous triplication redundancy processor can be reduced by at least one order of magnitude through the highly reliable decision strategy, and the processor reliability is improved, and on the other hand, the structural features of the heterogeneous triplication redundancy processor are masked by the output decision device, and with the combination of its heterogeneous redundancy, the heterogeneous triplication redundancy processor can well conceal its true structural information and increase the difficulty of attacking sniffing and implementation.