Belonging to the technical field of advanced ceramic preparation, the invention discloses a nanowire constructed SiC elastic ceramic and a preparation method thereof. The technical scheme includes: taking a porous carbon material or porous carbon fiber material as the skeleton, adopting a polysiloxane sol prepared by hydrolysis of alkoxy silane as the precursor, and carrying out impregnation-pyrolysis-gas phase reaction to obtain a porous carbon material or porous carbon fiber material/SiC nanowire intermediate structure, and then removing the porous carbon material or porous carbon fiber material skeleton by thermal oxidation so as to obtain the nanowire constructed SiC elastic ceramic. The material is a light three-dimensional network structure formed by self-assembly of SiC nanowire and has certain strength, good elastoplasticity and excellent thermal insulation properties. The method is a new method for preparation of elastic ceramics, can realize preparation of large size SiC elastic ceramics with a complex shape. Meanwhile, the preparation cycle is short and the cost is low, therefore the method is suitable for industrial production.