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Rapidly quenching embrittlement (RQE) sometimes appears in Fe73.5 Cu1 Nb3Si13.5B9nanocrystalline soft magnetic alloy (FINEMET) during production process. As a re-sult of RQE the ductility of the as-quenched ribbon drops seriously. The mechanism ofRQE has been elucidated in the recent works of current authors. It was believed thatRQE is due to the structural relaxation but not related to α-Fe(Si) crystallization. Inthis paper, the high resolution TEM (HRTEM) method and image digital processingwere applied to analyze the HRTEM images of two FINEMET rapidly quenched rib-bons with different thicknesses in detail. In the thinner ductile sample, the orderingdomains with the size of about 3nm are observed. In the thicker RQE sample, themetastable nanocrystalline domains with the size are 18nm are observed along with thestructural relaxation. These domains seem to have Fe3B-like metastable phase struc-ture on nanometer scale. The result indicates that the local atomic ordering regionsextend when RQE induced by structural relaxation occurs.