The invention discloses a high temperature-resistant ethylene-propylene rubber / silicone rubber blended rubber compound and a preparation method thereof. First silicone rubber undergoes roll banding on an open mill, hydroxy silicone oil, part of a filling reinforcing agent and part of a silane coupling agent are added, mixing is performed, the mixture is mixed with ethylene propylene diene monomer, and then the remaining filling reinforcing agent, the remaining silane coupling agent, plasticizer and an active agent are added to perform mixing; blanking is performed after thermal treatment; when the temperature of the mixture is lowered to normal temperature, the mixture undergoes thin-passing in the open mill; after the roll banding is performed, an anti-aging agent, an accelerator and a vulcanizing agent are sequentially added, a triangular bag is made and thin-passing is performed, and after uniform mixing, slices are generated. According to a white carbon black reinforcing system of the ethylene-propylene rubber / silicone rubber blended rubber compound, the interfacial compatibility of ethylene-propylene rubber and silicone rubber is improved while the appropriate silane coupling agent is selected to guarantee that white carbon black is dispersed well, the effect of the silane coupling agent is brought into maximum play through an appropriate mixing process, and the obtained rubber compound has good mechanical property and high temperature resistance.