Bulk (MgB 2) 0.96Ni 0.04 samples doping with premilled Ni powders were sintered at 750∈°C for 30 min. During sintering, liquid Mg-Ni phase prompts solid-solid reaction between Mg and B and the size of milled Ni powder determines the final distribution of the secondary MgNi 2.5B 2 phase in the sintered samples. A flux jump was observed in the (MgB 2) 0.96Ni 0.04 samples doping with Ni powders. Recognized from the measured superconductive properties, smaller-sized Ni powders can provide more effective flux pinning centers and thus improve the performance of the critical current density. © 2011 Springer Science+Business Media, LLC.