The invention discloses an iron core longitudinal magnetic field electrode structure for a vacuum arc-extinguishing chamber and an assembling method of the iron core longitudinal magnetic field electrode structure. The electrode structure comprises a plurality of horseshoe-shaped magnetic pole sheets which are stacked together; in two adjacent magnetic pole sheets, the opening angle of the upper magnetic pole sheet is larger than the opening angle of the lower magnetic pole sheet; and in each group of two adjacent magnetic pole sheets, at least two concave-convex structures which are matched with each other are adopted, so that the two adjacent magnetic pole sheets can be fixed together through the matching of the concave-convex structures. With the electrode structure adopted, on the one hand, the close matching between the magnetic pole pieces can be ensured, and gaps can be decreased, and on the other hand, a high-precision self-positioning effect is realized, and error-proof and fool-proof effects can be realized.