Abstract: The reliability of an actual load-sharing parallel system is greatly affected by total load of the system and load capacity of components. A failure rate variation model of components of unrepaired load-sharing parallel systems is established by analyzing the components' load capacity. Through Markov process, the universal reliability model of load-sharing parallel systems is established. According to the failure rate variation model and the relations between total load of system and load capacity of components, the universal reliability model is classified into ideal load capacity model, maximum load capacity model, and critical load capacity model. The reliability of these three models is derived in this paper. The models and calculation results are verified via case study the reliability analysis of parallel systems with independent components and m/n:(F) voting system.