Abstract: The effects of pulse potential,discharging times,Ni²⁺ concentration,pH value and rare earth additives(LaCl₃,NdCl₃) on the conversion ratio of Ni²⁺ as well as the structure,shape and average diameter of Ni-P nanopowders prepared by pulse discharging in solution were investigated by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),and focused beam reflectance measurement(FBRM).It is indicated that discharging energy is the key factor that influences the size of Ni-P nanopowders and the conversion ratio of Ni²⁺.With the increasing of pulse potential or discharging times,the average diameter of Ni-P nanopowders decreased while the conversion ratio of Ni²⁺ increased.The real-time monitoring results of FBRM showed that the velocities of nucleating and growing of Ni-P particles during the course of discharging were remarkably higher than those after discharging.The size of Ni-P nanopowders could be reduced by adding LaCl₃ or NdCl₃ to precursor solution.The average diameters of Ni-P nanopowders were 156 nm at the LaCl₃ concentration of 0.1 g·L^-1 and 72 nm at the NdCl₃ concentration of 0.05 g·L^-1,respectively.