Abstract Soft magnetic metallic materials are the key components in generators, motors and transformers. The Curie temperatures of currently used soft magnetic metallic materials limit their applications in high-temperature environments. In this work, we tuned the bcc/fcc ratio through modifying the Co content, thus obtaining near-zero magnetostriction and improved soft magnetic properties in the magnetostrictive system Fe100-xCox (70≤x≤93) alloys with high Curie temperature. With the increase of Co content, we observed the evolution of three crystal structures from bcc to fcc and three types of magnetostriction curves, ∧-type, ∨-type and M-type, which can be well interpreted by the domain-switching model. The optimum composition Fe20Co80, corresponding to the coexistence of bcc & fcc phases, exhibits magnetostriction of -3 ppm, a coercive field of 0.18 kA/m and saturated magnetization of 183 Am2kg−1. Our study provides an effective route to design magnetic functional materials with zero magnetostriction.