The invention discloses an Fe-Si-B-Nb-Cu iron-based amorphous / nanocrystalline soft magnetic alloy material and a preparing and heat treatment process. The Fe-Si-B-Nb-Cu iron-based amorphous / nanocrystalline soft magnetic alloy material comprises following composition elements including, by mass percent, 81 to 83% of Fe, 8.5 to 9.5% of Si, 1.5 to 2% of B, 3 to 4.5% of Nb, 1 to 2% of Cu, 1 to 2% of Mo, 0 to 0.5% of Ni and 0 to 0.5% of Cr. A small amount of metal elements of Mo, Ni and Cr is introduced into the Fe-Si-B-Nb-Cu system, the better amorphous forming capacity of the Fe-Si-B-Nb-Cu iron-based amorphous / nanocrystalline soft magnetic alloy material is ensured, through the heat treatment process, an alloy strip of an amorphous structure is obtained, in the strip spraying and heat treatment process, the oxidation resistance capacity is better, in the heat treatment process, atmosphere protection is facilitated, temperature consistency is improved, product performance discreteness is reduced, and the beneficial effects of being high in heat treatment efficiency and good in toughness are achieved.