Abstract: The conventional reliability model of parallel system is inadaptable to the parallel system where the load is transferred and shared. Analyzing the dependent failure and stepwise computing the reliability of a parallel system, the reliability model of cumulative fatigue damage of a load sharing parallel system is developed according to the total probability formula and Miner theory. Then, a simulative computation is done by the Monte Carlo method for the reliability of parallel system in which the service life of a component follows the Weibull distribution, with the explicit formula of system reliability deduced for the service life of a component that follows the logarithm normal distribution. As a result, a reliability model of cumulative fatigue damage for the parallel system under the action of varying stress is developed.