The invention discloses a Fe-Si-Al magnetic core preparation method and an inorganic composite insulation coating material for a magnetic core, belonging to the field of Fe-Si-Al magnetic material and used for solving the high eddy-current loss problem of existing magnetic cores and such problems caused by the fact that the existing magnetic cores usually use organic coating materials as stress is difficult to eliminate in a forming process, the insulation property of the material is poor, and the volatilization quantity of organics is large in heating processes such as heat treatment. The Fe-Si-Al magnetic core preparation method disclosed by the invention comprises the following steps: cast ingot smelting, powder making, surface phosphorization, insulation coating, compression moulding, annealing treatment and surface coating; the prepared Fe-Si-Al magnetic core has the advantages of low eddy-current loss, small magnetic conductivity temperature coefficient, good temperature stability, high direct current superposition characteristic, high saturation flux density and good high-frequency characteristic and meets the requirements for high frequency, small size, high power and electromagnetic interference resistance of electronic devices.