In order to solve the reliability and security problems which are caused by the structural alteration of the traditional steering system, the fault-tolerant control method for the Electronic Control Unit of Steer-By-Wire system is studied in this paper. A hardware structure of SBW, with triple cores and dual motors is present. And one triple-loop control system and a triple-core control mechanism which is coordinated by distributed processing mechanism and voting mechanism are proposed too. The communication among steering feeling motor, steering motor and cores is achieved through FlexRay bus. The Hardware-in-loop Simulations test result shows that the reliability and safely of the Electronic Control Unit of Steer-By-Wire system is effectively improved.