Since the traditional reliability evaluation method based on Markov model can't reflect the effects of complex and variable working conditions on the reliability of electronic system

a reliability evaluation method based on Markov model and cloud theory is proposed by combining Markov model with cloud model. Suitability cloud models of failure rate and repair rate are built according to the characteristics of environment and maintainers. Then working condition cloud models are made in terms of the real working conditions. The failure rate cloud and the repair rate cloud are generated from the suitability cloud models and the working condition cloud models through X condition cloud generator. Finally the failure rate cloud and repair rate cloud are used as input parameters of Markov model to evaluate the reliability. Since the effects of environmental conditions and physiological condition are taken into account in the proposed method

the reliability evaluation is more accurate than that of the method based on Markov model. Analysis of hot-standby system using the proposed method shows that the variation of conditions will cause 5% or fewer decline under good work conditions and up to 90% decline under bad work conditions

which is in accordance with the system's actual situation.