Mn70Fe30-xCox (x=0, 2, 4) alloys were prepared using non-consumable vacuum arc furnace smelting followed by subsequently solution treatment. The effect of Co content on the property of magnetic-field-induced strain (MFIS) was studied by means of X-ray diffraction (XRD), photomicrograph, differential scanning calorimetry (DSC), and resistance strain gauge method. Result shows that Mn70Fe30-xCox (x=0, 2, 4) alloys are of singe phase at room temperature. With the increase of Co content, the Nel temperatures of alloys decrease, which are all higher than room temperature, i.e., the alloys exhibit antiferromagnetic austenite microstructure at room temperature after quenching from high temperatures. Alloys possess much larger MFIS with the increase of Co content, and taking Mn70Fe26Co4 as an example, when the magnetic field strength is 1.1 T, the MFIS is at its maximum, 610-5.