Abstract: The natural circulation lead-bismuth cooled reactor is an important direction for the reactor development. Understanding of the natural circulation flow characteristics of lead-bismuth is crucial to the development of natural circulation lead-bismuth cooled reactor. Experimental modeling similarity research is one of the most extensive method for this. Based on the similarity theory, this paper adopts a combination of theoretical derivation and numerical simulation to explore the possibility of water to simulate the flow characteristics of lead-bismuth. Final results showed that the flow characteristics of lead-bismuth can be simulated by water successfully under steady state and transient state.