In the present work, the resistances to corrosion of heat treated soft magnetic alloy Fe81Cr17Si1.5TiBRe and untreated one have been comparatively studied, which were tested in neutral salt spaying tester, in 50%vol. hydrochloric acid (HCl) at 100 , in humidity thermal oxidation tester, specially in simulating oilfield waters containing sulfide ion (S2-) and without S2-. Heat treatment was carried out at 1150 for 4 hours under the protection of hydrogen gas. The results show that heat-treatment affect the magnitude of grain of Fe-base soft magnetic alloy and distribution of inclusions in grain and in grain boundaries. Heat treatment enhances anti-corrosion properties, i.e. resistance to chlorine ion (Cl-) corrosion of the alloys, resistance to humidity thermal oxidation corrosion, oilfield water corrosion. The electrochemical corrosion mechanisms of the alloy in oilfield waters are not affected by heat treatment. In simulating oilfield water, the passivity property of the alloy is affected by S2- or HCO3-.