The invention relates to a magnetic core of a low conductive magnet, a manufacturing method and and application thereof. The magnetic core of the low conductive magnet is made of ferromagnetic magnetically soft alloy, the molecular formula of the alloy is FeaMbCucSidBeM'fXg, wherein M represents Ni and / or Co, M' represents at least one element among V, Ti, Nb, Mo, Cr, Hf, Ta and W, and X represents P, Ge, C and impurities. With atomic percent as the unit, a, b, c, d, e, f and g meet the following conditions: b is larger than or equal to 5 and is smaller than or equal to 40, c is larger than or equal to 0.05 and is smaller than or equal to 1, d is larger than or equal to 1 and is smaller than or equal to 8, e is larger than or equal to 10 and is smaller than or equal to 20, f is larger than or equal to 0.5 and is smaller than or equal to 5, g is larger than or equal to 0 and is smaller than or equal to 0.5, d and e are larger than or equal to 10 and are smaller than or equal to 25, and a is equal to 100 minus b minus c minus d minus e minus f minus g. The microstructure of the using state of the alloy is an amorphous state. The magnetic core is low in magnetic conductivity, high in anti-saturation performance and high in modulation property to alternating current and direct current components. Further, a B-H loop line is of a linear shape, and the magnetic conductivity of the linear B-H loop line is high in modulation property in the alternating current and the direct current.