Maleic anhydride grafted linear low density polyethylene/graphene (LLDPE-g-MAH/G) nanocomposites were prepared by melt blending. The effects of different graphene content on the crystallization behavior, rheological properties and mechanical properties of LLDPE-g-MAH/G nanocomposites were investigated. The results show that with the increase of graphene content, the crystallinity and long period of the composites increase gradually, the storage modulus, loss modulus and complex viscosity increase first and then tend to be gentle, and the tensile strength and elongation at break increase first and then decrease with the increase of graphene content. When the graphene content is 0.5%, the mechanical properties of the nanocomposites are the best, and the tensile strength and elongation at break reach 26.8 MPa and 998%, respectively. When the graphene content is 0.5%, the polyethylene crystal and graphene in the stretched nanocomposites are oriented along the stretching direction at the same time, so that the original crystal in the nanocomposites is damaged and broken, the crystal size is reduced, and the melting point is reduced. The thermal conductivity of the nanocomposites along the tensile direction after stretching is 3.6 times that before stretching, and the thermal conductivity is greatly improved.