In this paper an efficient algorithm of system design with reliability approach is presented. Using this algorithm in subsystem designing of special systems may lead to systematically optimized design with reliability parameters attitude. By applying item tree parameters including general subsystem parameters into the algorithm and by knowing failure modes and the occurrence rate of each failure mode, the design may be improved and necessary reconsiderations can be applied in order to prevent or reduce the probability of failure mode. First some basic conceptual definitions including reliability, availability, capacity and failure rate is explained then various reliability analysis methods like Fault Tree Analysis (FTA), Failure Mode Effect Analysis (FMEA), Reliability Block Diagram (RBD) and Markov analysis is discussed. Reliability and availability distribution over different phases of unlocking and deploying mechanisms are illustrated using Windchill Solution. Subsequently the effect of the different ranges of failure rates of added components on reliability, availability and capacity of whole system is investigated. By analyzing the reliability and availability of system for different phases, it was found that the whole system is under stable situation at the end of each phase. Also results showed that the reliability, availability and capacity of whole system increased and reached a stable level by minimizing the failure rate of the redundant components.