The invention discloses a heat-resistant alloy monofilament and a preparation method thereof. The alloy monofilament comprises the following components of, in percentage by mass, less than or equal to0.03wt% of B, 0.5wt%-1.2wt% of Mg, 0.1wt%-0.2wt% of Ti, 0.05wt%-0.1wt% of rare earth elements, and the balance Al and inevitable impurities. According to the heat-resistant alloy monofilament and thepreparation method, industrial aluminum ingot with the purity of more than or equal to 99.7% is used as a raw material, and the microstructure and the comprehensive performance of the alloy are improved mainly through the addition of trace Mg, Ti, B and rare earth elements, and a treatment process is optimized, so that the heat-resistant alloy monofilament with the electrical conductivity of morethan or equal to 61% IACS (20 DEG C), the tensile strength of more than or equal to 160 MPa, the elongation of more than or equal to 2.0%, the long-term heat-resistant temperature of more than or equal to 120 DEG C, and the strength persistence of more than or equal to 90% under the condition of heat preservation at 210 DEG C for 1 h is developed.