This paper investigates a class of fault detection problems for time-varying sampling networked control systems with uncertain packet dropout rate via delta operator. Packet dropout occurs during sensor-to-controller and controller-to-actuator data transfer, the packet dropout model is represented by two independent Bernoulli random variables, assuming that the packet dropout rate is uncertain in the sensor-to-controller channel, and its mean consists of the constant and uncertain value. Time-varying sampling periods are described by finite length switching sequence, which can reduce conservativeness. The sufficient conditions which can guarantee the asymptotical stability of the augmented system with ${\textstyle H_{\infty