IEC 61508 standard could be used in the evaluation of safety of the k-out-of-n technical systems, including elements which may remain in one out of four different reliability states. Such a model leads to the huge complexity of analytical calculations and the limitations of its practical application possibilities. Therefore, a computerised method using Markov processes for estimating the reliability of k-out-of-n systems was developed. The algorithmization of the applied computational procedure was performed. It allowed one to analyse systems including a huge number of elements. An algorithm that may be applied for complex k-out-of-n systems was developed and used for exemplary calculations. The developed method was verified by comparing the obtained results with the ones obtained from analytical method as well as simulation method. The compatibility of results obtained in the two methods confirms the correctness of the developed procedure and proposed computer program which now offers the possibility of doing calculations for k-outof-n structures with more than three elements required for the system’s proper functioning and significantly accelerates calculations. Reliability and safety are priorities in the operation of technical systems. This decides of the applicability of the calculation methods described. The operational safety aspects are of particular significance in cases when the occurrence of a failure is a hazard to people’s health and life, ecological risk or considerable financial loss.