The invention relates to a flower-shaped MoS<2>@graphene nanocomposite and a preparation method therefor. The nanocomposite is prepared by adopting a one-step hydrothermal synthesis method; graphene oxide, sodium molybdate and sulfourea are taken as the raw materials, and purified water is taken as the solvent; and then the flower-shaped and uniformly-loaded MoS<2>@graphene nanocomposite is obtained under the auxiliary effect of glucose or glucosamine hydrochloride. A TEM/SEM result proves that the ultra-thin MoS<2> nanosheets form the special flower shape, and are loaded to the high-quality graphene in a mono-dispersion manner; and an XRD spectrogram can prove that the MoS<2> is good in crystallization, and belongs to a hexagonal crystal system 2H-MoS<2> crystal phase. The graphene nanocomposite is simple in process, controllable in conditions, and high in load uniformity of the materials; and the prepared MoS<2>@graphene nanocomposite has a wide application prospect in the fields of new energies, such as the negative electrode material of lithium ion batteries, and the like.