Fluorine/silicone composite rubber is widely used as a sealing material in aerospace, missile, automotive, petroleum, and other industries, but the traditional process does not use synergistic fillers to strengthen the composite system. In this research, fumed SiO2 and black caron (N990) were used as synergistic fillers, fluorine/silicone composite rubber was prepared by mechanical mixing process, and three different fluorine rubber systems were used to find the best composite material. The mechanical properties, thermal properties, aging properties, moderate strength properties, and microstructure of the composites were evaluated. Studies have shown that mixing the two can produce a certain interface interaction and effectively improve the compatibility. The physical properties of the material tended to decrease during the increase in the added amount of silicone rubber (MVQ). The maximum tensile strength of the hybrid material can reach 15 MPa. The optimal mixing ratio is fluororubber/silicone rubber (FKM/MVQ) = 9/1. At this time, the mechanical properties of the composite material are in the best state, and SiO2 and black caron (N990) have a reinforcing effect, which can effectively improve the mechanical properties. After the composite was kept at 200 °C for 48 h, the tensile strength and elongation of the best sample A1 were 99.5 and 97.0%, respectively, showing excellent anti-aging properties. This work provides a method to fabricate high-strength fluorine/silicone composites using synergistic fillers that may be used in heat-medium-sealed environments.