Abstract: As the environmentally friendly and recyclable cable insulation materials, polypropylene (PP) has attracted wide attention due to its excellent electrical and heat resistance properties. Besides the DC voltage, the operating impulse overvoltage often occurs in HVDC cable. At the same time, the change of cable temperature affects the electrical conductivity and space charge accumulation of insulating materials, which leads to the distortion of electric field in insulating materials, leading to the initiation of electrical trees. In this paper, the growth characteristics of polypropylene and crosslinked polyethylene were compared under the same conditions. The effects of DC-pulse combined electric field and temperature on the growth characteristics of polypropylene were analyzed, and the mechanism of different methods to restrain the electrical tree was discussed.