The invention discloses a dynamic vulcanized fluoroplastic / fluororubber / silicon rubber thermoplastic elastomer and a preparation method thereof. The thermoplastic elastomer comprises the following raw materials in parts by mass: 10-80 parts of fluoroplastic, 5-80 parts of fluororubber, 5-85 parts of silicone rubber, 1-10 parts of acid acceptor, 1-20 parts of interfacial modifier, 0.1-5 parts of cross-linking agent and 0.1-10 parts of cross-linking aid. The preparation method comprises the following steps of: uniformly mixing the fluoroplastic, the fluororubber, the acid acceptor, the silicon rubber and the interfacial modifier at 175-330 DEG C; and adding the cross-linking agent and the cross-linking aid under a high-speed shear condition to carry out dynamic vulcanization on rubber to obtain the thermoplastic elastomer. The fluoroplastic / fluororubber / silicon rubber thermoplastic elastomer has high mechanical strength, has the characteristics of excellent high-temperature and low-temperature resistance, chemical resistance, oil resistance, capability of repeated processing and the like and can be widely applied to the fields of aerospace industry, automobile industry, information and electronics industry, chemical industry, new energy resources, electric power industry, environmental protection and the like.