Abstract: In order to explore the influence of Ni-coating thickness on the thermal residual stress in AZ91D magnesium matrix composite reinforced with Ni coated carbon nanotubes(Ni-CNTs/AZ91D), the distribution of the thermal residual stresses in Ni-CNTs/AZ91D composite was simulated by using finite element method(FEM)based on some experiments. The results indicate that plating Ni on CNTs’surface can greatly reduce the thermal residual stress of Ni-CNTs/AZ91D. For the Ni-CNTs/AZ91D composite materials, the thermal residual stress achieves the minimum at the thickness of Ni-coating is 6nm. While the thickness of Ni-coating is varying from 2nm to 6nm, the thermal residual stress is diminished with the increase of the thickness of Ni-coating. Once the thickness of Ni-coating is larger than 6nm, the thermal residual stress increases with increasing the thickness of Ni-coating. Moreover, the location of thermal residual stress’s maximum moves toward the interface of Ni-coating and substrate with increasing of the thickness of Ni-coating.