Software defined networking(SDN)and network function virtualization(NFV)as new tech-nologies have shown great potential in improving the flexibility of resource management for network service provisioning.As traffic dynamics may cause violation of rigid service requirements,especially for ultra-reliability and low-latency communication(URLLC)service,it is essential yet challenging to dynamically allocate an appropriate amount of resources(including computation,transmission,and energy)to network functions(NFs)in softwarization-based networks.Meanwhile,with the explosion of high resource-demanding applications,the energy efficiency of communication networks deserves significant attention.In this paper,we investigate the dynamic network function resource allocation(NFRA)problem with aim to minimize long-term energy consumption while guaranteeing the requirements of URLLC services in softwarization-based networks.To cater for efficient on-line NFRA decisions,we design a distributed dynamic NF resource alloca-tion(DDRA)algorithm based on dynamic value iteration(DVI).The convergence of the DDRA algorithm is proved.We conduct simulation experiments based on real-world data traces for performance evaluation.The numerical results demonstrate that the proposed DDRA algorithm achieves around 25％and 20％energy consumption reduction when compared with two benchmark algorithms,respectively.