Abstract: Taking a design of city gas transmission network in the Pearl River Delta for example, concludes design problems in city gas transmission network. As city gas transmission network has a characteristics of multi-distribution points, multi-branches and large quantity of distribution volume, analyzes the effect of engineering investment on building gas transmission pipeline. Points out that if booster transmission is required, location selection of compressor station will affect engineering investment and economic benefit directly. For the project build by stage and the trunk line about 300 km in length, increases pipe diametei properly is superior over increasing number of compressor stations in the aspect of engineering investment.