Abstract: Fault injection is an effective technique for the validation of fault tolerant computer systems. In this paper, the function of layer decomposition model in the fault injection experiment is analyzed and MBDT——a decomposition model of fault tolerant system based on dynamic fault tree is introduced. The methods of producing attribute sets of fault injection experiment using this model are discussed in detail. An experimental strategy of fault injection for the whole validation of fault tolerant computer systems is finally constructed. This strategy has been applied to the hardware implemented fault injection tool——HFI3 and a space flight fault tolerant computer is validated. The experimental results are presented to demonstrate the effectiveness of this strategy.