The invention belongs to the technical field of alloyed soft magnetic powder core and particularly relates to a preparation method for an iron-based amorphous magnetic powder core with ultrahigh magnetic conductivity. The preparation method includes the steps of 1), subjecting an iron-based amorphous thin belt to heat treatment; 2), smashing the iron-based amorphous thin belt to obtain iron-based amorphous powder; 3), subjecting the iron-based amorphous powder to screening and matching, and then mixing the same to mixed powder containing coarse powder and fine powder; 4), subjecting the mixed powder to passivating, coupling, insulation coating and lubricating treatment in sequence by adopting passivator, coupling agents, insulating compounds, binding agents and lubricating agents, and then pressing for forming; 5), subjected the formed magnetic powder to annealing treatment and spraying insulation treatment in sequence. By the method of mixing and coupling treatment upon the coarse powder and the fine powder, the problem about pressing large-particle amorphous powder for forming can be effectively solved, and the iron-based amorphous magnetic powder core with the ultrahigh magnetic conductivity more than 200 can be prepared.