The invention discloses a preparation method for a heat-resistant component containing an embedded runner, of a fusion reactor blanket. The structural material of the component is reduced activation martensitic/ferritic steel, the embedded runner is formed by virtue of a scheme of explosive welding for a bottom plate and a cover plate of a milling groove, and through filling a runner groove with a low-melting-point metal and a carbon steel plate, runner deformation due to an explosive shock wave is reduced and a good welding effect is ensured, and later heating removal at a low temperature is facilitated; and meanwhile, a layer of nano-oxide-reinforced reduced activation martensitic/ferritic steel is formed at the outer side of the component through explosive cladding to increase the maximum service temperature of the component, and buffer layers are added between explosives and the nano-oxide-reinforced reduced activation martensitic/ferritic steel to prevent the plates from cracks. The method is capable of realizing combination for the bottom plate and the cover plate of the milling groove, and the nano-oxide-reinforced reduced activation martensitic/ferritic steel in one process, and capable of effectively increasing the preparation efficiency of the large heat-resistant component of the blanket, and ensuring the stability of the microstructure of the material during the preparation process for the component.