The high voltage cable, especially the extra high voltage XLPE cable in the transmission operation once the breakdown, will cause great damage to the power grid, causing great losses to the country. At the same time, enterprises in the manufacturing process, once the cable partial discharge standard value (PC value) exceeded, or even withstand voltage test breakdown, the economic losses caused to the enterprise is also very great. Based on the theory of electric breakdown, this paper analyzes and studies the manufacturing process of high voltage XLPE cable in theory and practice, and finds out the key points that lead to high voltage breakdown and partial discharge standard value exceeds. Such as:Conductor burr; Electrical conductivity of conductor semi conductive shielding tape; Bump and scratch of extruder die; Bump and scratch of extruder runner; Cleaning and storage of material; Number and size of micro pore in insulation layer, and internal stress in insulation layer and so on. Through the analysis of these easily overlooked, but also extremely important part of the manufacturing process, the control method is given, in order to achieve the purpose of reducing partial discharge and breakdown frequency, improve the overall quality of high voltage XLPE cable.