Abstract: MnZn ferrite U-shaped magnetic core parts were prepared by Micro-forming fields activated sintering technology(Micro-FAST), and the effects of sintering temperatures on the density, phase and microstructure of MnZn ferrite magnetic cores were investigated. The results show that in the sintering temperature range of 850℃-1000℃, with the increase of sintering temperature, the density and the spinel content of the samples increase first and then decrease. Under the process parameters of sintering temperature 900℃, holding time 480 s, heating rate 20℃/s, applied pressure 70 kgf and cooling rate 5℃/s, MnZn ferrite magnetic core prepared by Micro-FAST has the maximum density of 4.95 g/cm3.