Ultraviolet transparent silicone rubber with different content of branched vinyl silicone oil was prepared by heat curing method. Curing process, mechanical and optical properties of modified silicone rubber were investigated by rotational rheometer, differential scanning calorimeter, electronic creep testing machine as well as ultraviolet and visible spectrophotometer. Crosslink density of silicone rubber was determined by the toluene-swelling method. Experimental results show that silicone rubber can form an effect of concentrative crosslinking in the presence of branched vinyl silicone oil. When adding certain amount (2 wt%) of branched vinyl silicone oil, the silicone rubber exhibited good mechanical properties (tensile strength 6.51MPa, enlongation at break 229.8%). Gel time and crosslink density of silicone rubber increased with the increase of branched vinyl silicone oil, while the UV transmittance of silicone rubber decreased as the loading of branched vinyl silicone oil increased. In conclusion, silicone rubber has excellent mechanical and optical properties (UV transmittance can be up to 92% and 89% at 350 nm and 300 nm, respectively), when the content of branched vinyl silicone oil is 2 wt%.