Breakdown and surface flashover are likely to occur on silicone rubber in the complex operation environments of electrical system. Firstly

silicone rubber specimens were treated by ultraviolet irradiation in vacuum for 24 hours

and DC breakdown and surface flashover characteristics of treated and untreated specimens were tested. Then

the activation energy and relaxation time distribution were calculated by dielectric relaxation spectroscopy. The trap characteristics were analyzed by surface potential decay. Finally

the chemical reaction of silicone rubber molecular chains was characterized using infrared spectroscopy. The results indicate that the molecular chains of silicone rubber crosslink via ultraviolet irradiation in vacuum

the activation energy of dipolar orientation polarization increases

while the molecular chain relaxation time decreases and molecular chain dynamic is hindered

which can improve the trap level and suppress the charge transport process of silicone rubber. DC breakdown strength and surface flashover voltage will increase by 2.38% and 8.79%

respectively. The molecular chain dynamic and charge transport process of silicone rubber

which is irradiated by ultraviolet in vacuum of which pressure is lower than 5×10-4 Pa for 24 h

are suppressed

thus the DC breakdown and surface flashover characteristics will be enhanced efficiently. The results can provide references for solving breakdown and surface flashover in silicone rubbers.