Subnetwork reliability is a key practical indicator for evaluating the fault tolerance of multiprocessor interconnection networks. The (n, k)-star networks \(S_{n,k}\) is an attractive generalized interconnection network. Existing studies on subnetwork reliability of \(S_{n,k}\) mainly focus on \((n-1, k-1)\) -dimensional subnetworks, while the reliability evaluation for general \(S_{n-m,k-m}\) subnetworks with arbitrary \(m\ge 1\) still remains insufficient, restricting the practical application of \(S_{n,k}\) in multiprocessor systems. To fill this research gap, this paper investigates the subnetwork reliability \(R_{n,k}^m(p)\) , defined as the probability that \(S_{n,k}\) contains at least one fault-free \(S_{n-m,k-m}\) subnetwork under independent vertex failure model. We derive the upper and lower bounds of \(R_{n,k}^m(p)\) by analyzing the intersection characteristics of subnetworks, and develop a heuristic algorithm based on Monte Carlo simulation to estimate the reliability. When the gap between the two bounds is sufficiently small, the Monte Carlo simulation result can well approximate the exact subnetworks reliability of \(R_{n,k}^m(p)\) , which provides an efficient approximate evaluation scheme without exhausting complex intersection enumeration.