Abstract: Aiming to the complexity of reliability model of Distributed Control System (DCS), a novel reliability modeling method has been put forward in this study. The method can be employed in many situations, especially in the case of DCS of electric power stations. The traditional reliability principles and the relative definitions of coherent system have been introduced as the foundations. Based on the structural and functional analysis of classical DCS, the overall structure of DCS which are normally seen as a repairable system in the real industrial productive process can been modeled as an un-repairable system according to some proposed approximating conditions. As an example, one whole DCS and its subsystems have been tackled to calculate their reliability indices. At the same time, one type of structure importance of DCS has also been computed based on the model. The values are of significant directive functions for the maintainance schemes of DCS.