Abstract: The instrumentation & control design features of DAS (diversity actuation system), including general design requirement, diversity signal transmission route, diversity processing technology, prevention of DAS spurious actuation and prevention of DAS actuation under the condition of RPS without SWCCF (software common cause failure) were analyzed in this paper. As a result of the analysis, features between two diversity signal transmission routes were presented and advantages and disadvantages of the bellow three diversity technology were discussed. The 2/2 internal logic arrangement of DAS cabinet was recommended. The regulation of set point values and response time combined with blocking DAS actuation from device status feedback signal is taken as a reference for prevention DAS actuation when RPS SWCCF is not appeared.