This paper explored a solid-phase reduction method to prepare ultrafine nickel powder under different conditions. The effect of a NaCl separator agent on the morphology, primary particle size and specific surface area of the prepared nickel powder is discussed. The results show that direct contact among primary Ni particles can be effectively inhibited during the reduction of nickel oxalate due to the presence of the NaCl separator agent. An ultrafine nickel powder with a primary particle size of between 80 and 150 nm can be prepared with NaCl as the separator agent at temperatures from 400 degrees C to 460 degrees C. The powder reduced at 430 degrees C has a uniform particle distribution and a decreased amount of agglomeration. (c) 2020 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights reserved.