Wireless sensor networks (WSNs) have important applications in many fields such as medical treatment and industry. WSNs typically consists of a large number of sensor nodes that rely on limited power supply in many applications. Therefore, improving the energy efficiency of WSNs has become an important research topic. As a basic service in WSNs, network flooding has the advantage that information can be distributed quickly and reliably in the whole network. However, due to a large number of redundant transmissions in the network, the energy efficiency of network flooding is low. We use the connected domination set (CDS) to improve the energy efficiency of network flooding by reducing the number of transmissions. A flooding protocol based on CDS, named CONE, is proposed. CONE inhibits nodes that are not in the CDS from rebroadcasting packets during the flooding process. In the simulation experiments, CONE performance is evaluated by comparing it with the baseline protocol. The experimental results show that the method improves the end-to-end reliability and reduces the duty ratio of network flooding. It is able to effectively decrease the average energy consumption.