Preforms were prepared with commercial carbon nanotubes、Ni-CNTs and Al with the mass ratio of 1:5.Then the CNTs/AlSi7Mg composites were produced by immersing the preforms into the aluminum alloy melt with bell jar.The ambient mechanical properties of the composites were tested

and the structure and tensile fracture morphology of the composites were observed and analyzed by X-ray diffractometry（XRD）、scanning electron microscopy（SEM）and energy dispersive spectrum analysis（EDS）.The results show that with CNTs addition

the grains of the composite can be refined

and the secondary dendrite arm space of the composites is reduced.Meanwhile

the tensile strength

the microhardness and the elastic modulus of the composites are improved significantly.The tensile strength

the micro-hardness HV and the elastic modulus of the composites with 1.0%CNTs reach 306MPa、118.0 and 132GPa

respectively

increased by 33.4% 、25.5%and 53.9%

respectively

compared with those of the matrix alloy.The fracture of the composites is characterized by quasi-cleavage type brittle fracture.