In this paper a novel multi-functional composite with high electrical conductivity and excellent magnetic field sensitivity was fabricated by embedding carbon nanotubes (CNTs) and carbonyl iron powders (CIPs) into shear-stiffening gel (STG). Oscillatory shear test demonstrated its excellent rheological properties. When the mass fractions of CNTs and CIPs were 1 wt% and 50 wt%, the increase in storage modulus (G') reached 585% under 100 Hz oscillatory shear and 428% under 1.2 T magnetic flux density with respect to its initial state. The resistivity of this CNT-CIP-STG composite achieved 25 Omega m and showed strong dependence on the magnetic field. When the external magnetic flux density was 873 mT, the normalized electrical resistance response reached up to -40.5%. Linearly increasing and step magnetic field was employed to study the electrical and mechanical behaviors of this CNT-CIP-STG composite. The instantaneous response and time effect were discussed. Interestingly, oscillatory shear showed limited influence on the electrical conductivity but notable enhancement on the sensitivity to magnetic field. A mechanic-electric coupling mechanism was proposed to illustrate enhancement of shear thickening effect and sensibility to magnetic field.