β-Ni(OH)2 was prepared by hydrothermal reaction，and then by hydrothermal reduction,Ni/β-Ni(OH)2 nanocomposite was obtained.The phase structure,morphology and chemical composition of the asprepared nanocomposites were characterized by XRD and SEM The friction and wear properties of the nanocomposite as lubricant additive in PAO6 based oil were evaluated by a fourball tribometerAfter tribotest,the surface morphology and chemical composition of the wear surfaces on the contact steel balls were analyzed by SEM and energy dispersive spectrometer (EDS) to illustrate the antiwear and frictionreducing mechanism of the resulting Ni/β-Ni(OH)2 additive.The results show that Ni/β-Ni(OH)2 nanocomposite as lubricant additive exhibits superior antiwear and frictionreducing ability.The tribological properties of the oil dispersed with Ni/β-Ni(OH)2 nanocomposite are much better than that of the based oil and the oil dispersed with β-Ni(OH)2The friction coefficient and wear scar diameter of the oil dispersed with 0.1% Ni/β-Ni(OH)2 are reduced by 17.6% and 41.5% respectively,as compared to the PAO6 oil.The superior tribological properties of Ni/β-Ni(OH)2 are ascribed to the special composite structure from the nanocomposite,the nano-Ni and layered β-Ni(OH)2,which leads to synergistic lubricating action produced between nano-Ni and β-Ni(OH)2.