NiFe 2 O 4 ultrafine powder with high crystallinity has been prepared through a reverse microemulsion route. The composition in starting solution was optimized, and the resulting NiFe 2 O 4 was formed at temperature of around 550-600°C, which is much lower than that observed from the solid-state reaction. Magnetic investigation indicates that samples are soft-magnetic materials with low coercivity and with the saturation magnetization close to the bulk value of Ni ferrite.