Abstract: Designed water application ratio is an important parameter which influences the investment and cost of the drip irrigation system, the water supply situation of crop and finally the benifits of the system. Generally, designed water application ratio has influence mainly on the field pipe network of the system. The influence of water application ratio on the cost of the drip irrigation system is evaluated by analysis of the relationship between the water application ratio and the quantity of the lateral and the submain pipes (PE) , as well as the annual cost of the field network. This can be a reference for the selection of the designed water application ratio.