Abstract This paper deals with possibilities of using genetic algorithms in design of costs optimization, which are needed to reach given reliability of technical system, respectively system reliability optimization by given amount of investment costs. In following chapters, there is a described design of new method, which will be later implemented in application and verified on an example. Causal relationships between system failures and elements faults can be detected by analytic approach, when at first the undesired system fault is identified and its reasons are progressively detected. The reliability of system and its elements is analyzed using method FTA (fault tree analysis) and system is represented by fault trees. In order to optimize costs, respectively reliability, the genetic algorithms are used.