Abstract: FeSiBCrC amorphous alloy powder with 6 particle sizes were prepared by a new industrial gas-water atomization and the amorphous magnetic core were prepared, which study the effects of particle size and annealing temperature on the properties of the magnetic core. The results show that the FeSiBCrC alloy powder with particle size D50≤25 μm are all amorphous, and the width of the supercooled liquid phase region ΔT can reach 40 ℃, which indicates that the FeSiBCrC alloy powder has strong amorphous formation ability. The saturation magnetization Ms and coercivity Hc of amorphous powders increase with the increase of particle size. The Ms value of A5（D50=5 μm）is 144.6 emu?g-1, and the Hc value is 1.8 Oe. However, the Ms value of A30 （D50=30 μm）is 152.6 emu?g-1 and the Hc increases to 9.8 Oe. The permeability μe of amorphous magnetic cores with different sizes has good stability in the frequency range of 0.1~600 kHz, and the fine powder phase is better than the coarse powder. The magnetic loss Pc of all amorphous magnetic cores increases with the increase of frequency. The finer the particle size, the more obvious the effect of annealing on reducing the magnetic loss Pc, in which the A5 (D50=5 μm) is decreased by about 84%, while the A30 (D50=30 μm) is only decreased by about 30%. After annealing at 500 ℃, the A5 (D50=5 μm) magnetic loss Pc reaches a minimum value of 578 mW?cm-3.