Formation and growth of the intermediate phases in the Ni-Al diffusion couples prepared by pouring technique were investigated.Electron probe microanalysis,scanning electron microscopy and X-ray diffraction were used to characterize the product phases in the joints.The results show that two intermediate phases form in the sequence of NiAl_3 and Ni_2Al_3 during solidification. After annealed,Ni_2Al_3 and NiAl_3 still exist in the joints of the couples.The reasons for the formation of Ni_2Al_3 and NiAl_3,as well as the absence of NiAl,Ni_5Al_3 and Ni3Al were discussed,respectively.The growth kinetics of both product phase layers indicates that their growth obeys the parabolic rate law. The activation energies and frequency factors for NiAl_3 and Ni_2Al_3 phases were also calculated ac-cording to the Arrhenius equation.