Abstract: According to the practice of reliability design of aeroengine digital control system,a new method, probability Resolving Method of Markovian State, is provided to deal with the first kind Markovian model of non-maintainable, non-combinational and non-redundant system. A practical application of this method to reliability design and calculation is presented through an actual example. In comparison with Markovian signal flow chart method and numerical method in solving the Markovian model, the present method is quite simple and clear in physical concept, and easy to calculate not only manually but also on computer. The fact that the results obtained from these three methods are identical proves the correctness of the provided method.