Coating soft magnetic powders by an insulation layer is an effective way to improve the high-frequency performance of soft magnetic powder cores. The quality of insulation coating is highly dependent of the coating materials and the coating method. In the present work, a commercial amorphous powder (Fe73Si11B11C3Cr2) was primarily coated by a PDA/PEI layer by a co-deposition method in alkaline solution. A thick PDA/PEI layer with good homogeneity was co-deposited on the surface of amorphous soft magnetic powders. The high frequency core loss of magnetic powder cores was reduced by up to ~44% at the magnetic induction of 0.1T and the frequency of 100kHz by primarily coating the amorphous powders by PDA/PEI. Microscopic images showed that the PDA/PEI coating layer on the amorphous powders does not peel off while being compressed. These results indicates that PDA/PEI insulation coating is a coating method which can effectively improve the comprehensive magnetic properties of magnetic powder cores. Display omitted •Thick PDA/PEI primary coating layer deposited on amorphous soft magnetic powders•Coating layer with cross-linked 3D network structure and uniform thickness•Strong adhesion to powder surface without peeling off•Excellent soft magnetic properties of powder core in high frequency