Abstract: During the design process of high reliable processor, appropriate fault injection technologies should be adopted at different stages to analysis and evaluation the reliability of the processor.On the basis of LEON3 high reliable processor, the simulation-based fault injection has been used to inject faults into Triple Module Redundancy flip-flops.Experiments show that the simulation-based fault injection can be used in the early design stage of high reliable processor to shorten the development cycle and reduce the cost of validation.