Abstract: Chengdu Metro Line 13 is an urban express line with the line grade speed of 140 km/h, which adopts the AC 25 kV power supply mode and needs to set electric split phase. In the electric split phase section, train needs to power off and slide through, the speed loss caused by which impacts the operation to certain extent. Combined with traction calculation, the influence of electric split phase setting on speed is analyzed, as well as the requirements for line slope and station spacing. By optimizing the horizontal and vertical sections of the line, it has been achieved that the speed loss of train passing through three electric split phases of the line are all less than 10%. Based on the design experience of Chengdu Metro Line 13, several important principles for setting the location of electric split phase of urban express line are put forward.