Abstract: Most water distribution networks (WDNs) in China have been in continuous operation for decades. The pipe deterioration is becoming increasingly prominent, posing a key factor affecting the functional reliability of WDNs. This study proposes an efficient analytical framework for assessing the time-varying reliability of WDNs considering pipe deterioration. First, a pipe failure probability prediction model based on artificial neural networks (ANNs) is utilized to evaluate the pipe mechanical deterioration. Then, a failure simulation model based on leaks and bursts is established, wherein a time-dependent roughness model is adopted to characterize the time-varying deterioration process of pipe hydraulic performance. Finally, the operational reliability of the WDNs is analyzed by integrating the probability density evolution method (PDEM). This framework is applied to calculate the operational reliability of a real-world WDN at different service years. The study results demonstrate that the deterioration effect significantly impacts the reliability of WDNs. Moreover, the proposed framework enables the operational reliability analysis of WDNs considering pipe deterioration while ensuring computational accuracy and efficiency simultaneously.