The invention discloses a composite structure magnetic circuit and a preparation method thereof, and belongs to the technical field of soft magnetic materials. A high-permeability soft magnetic alloy is compounded with a soft magnetic alloy with high saturated magnetic induction density to form the composite structure magnetic circuit. An electrode head made of materials with high saturated magnetic induction density is compounded in the magnetic circuit and close to an air gap, so that magnetic flux in the magnetic circuit can be concentrated at the electrode head, flux leakage is decreased, and the magnetic induction density of the air gap is improved. The high-permeability soft magnetic alloy 1J50 and the soft magnetic alloy 1J22 with the high saturated magnetic induction density are compounded together by means of machining, welding and forging, the magnetic induction density of the air gap of a compounded device can reach more than 1.6T, the problem of low magnetic induction density of the air gap of a device made of a single alloy is solved, and the magnetic circuit can be used for a filter, an electromagnet, a micro-motor, a relay and the like.