This paper presents a discussion on economic principle of the gauging station network design forthe large and medium rivers Aiming at the,accuracy of the interpolated yearly runoff and its economic benefit ana-lysis,a relational expression of accuracy- economics is established by the network density related to their accura-cies of yearly runoff. Some example,of main river control stations in upper reach of the Yellow River and regionalrepresentative stations in the Jinghe River Basin are given to verify the rationality about the relational expressionof accuracy-economics.The proposal is to provide an idea and a method that determine the network density andits accuracy criterion under economic principle.