The present disclosure relates to a dense boron nitride ceramic with high plasticity and high elasticity and the preparation process thereof. The preparation process includes the following steps: A) weighing a predetermined amount of spherical boron nitride nano-powders with onion-like structure, pre-pressing them into a pre-pressed body and putting the pre-pressed body into a sintering mold; B) putting the pre-pressed body obtained in step A) together with the sintering mold into a spark plasma sintering apparatus or a hot-pressing sintering apparatus for sintering; and C) taking out the mold after cooling, and removing the mold to obtain the boron nitride dense ceramic block with high plasticity and high elasticity. According to the present invention, a boron nitride ceramic with high strength and high plasticity is obtained via sintering spherical boron nitride nano-powders with onion-like structure.