Abstract: Voltage level selection is important to economy of high voltage distribution network. Load density has high correlation with voltage level selection. At present, related research has no quantitative relationship investigation between load density and voltage level selection.Aiming at the aforementioned problem, this paper analyzes quantitatively load density’s impact on voltage level selection, identifies voltage-droop’s great constraint on power supply capability of 110kV/10kV substation. Meanwhile, this paper infers quantitative relationship between power supply limit and load density, and establishes economy analysis models of 110kV one-level voltage step-down mode and two-level voltage step-down mode. Load density threshold for determining economy performance of two modes is also inferred and can be used as reference for voltage level selection. Case studies based on the distribution network in a province is carried out and the result indicates that the cost will be reduced and the economy performance will be improved by using the proposed method.