Abstract: Abstract: The voltage at the terminal of the medium voltage distribution line with heavy load and big power supply radius is often difficult to meet the national standards. This paper firstly conducting compensation analysis in distribution line, introducing the series compensation optimization model for distribution network. Next, proposing a method to determine the series compensation line candidate. Then, a method is proposed to calculate the value range of series capacitance in distribution line. Fast and elitist non-dominated sorting generic algorithm (NSGA-II) is used to solve the multi-objective optimization model of series compensation. The calculation results of examples show the effectiveness of the model and method.