Diversity Actuation system (DAS) is an important role in defense in depth design of nuclear power plant, it needs to maintain sufficient diversity with the reactor protection system (RPS). The technical principles of simple hardware technology and digital technology are different, which is a good solution for DAS. But there are several disadvantages in traditional simple hardware, such as the self-diagnosis coverage is very low, and the DAS can not achieve the logic degradation automatically based on sensor and acquisition channel fault. This paper proposes a logic degradation design scheme based on simple hardware technology. The logical degradation based on sensor and acquisition channel fault can be realized, and reliability analysis and test verification show that the scheme can solve the above problems with simple hardware technology, and the scheme has been applied to the Taipingling 1&2 project (HPR1000), and also can be applied for modification of nuclear power plant in operation, which has a broad market prospect.