Abstract In the reliability investigation of large-scale systems, the problem of the complexity of their reliability functions arises. This problem may be approximately solved by the assumption that the number of system components tends to infinity and finding the limit reliability function of this system. In this paper, a three-element closed class of limit reliability functions for a regular homogeneous series-parallel system is fixed. The system is such that the number of its series components is of less order than the logarithm of the number of its parallel components. Moreover, some examples of the considered systems and their limit reliability functions are given. The results may be useful in the reliability evaluation of large homogeneous systems and may be the origin in the reliability investigation of large nonhomogeneous systems.