The invention discloses a preparation method of a high-temperature superconducting line. A plurality of strips are stacked together and welded into the high-temperature superconducting line in a hot dip coating manner. The preparation method particularly comprises the following steps: fixing each strip on a pay-off device and positioning center lines of the strips; conveying each strip into a solder furnace by a method of loading unreeled strips in unreeling spools; and positioning all strips in the solder furnace through idler wheels, welding and merging the strips into a line and drawing a charge to obtain the high-temperature superconducting line. The prepared high-temperature superconducting line is round or square, is high in critical current and suitable for bending and twisting, has relatively high physical strength and is not easily damaged; an external magnetic field sensed by a superconductor can be reduced; the critical current attenuation and the AC loss can be reduced; and the prepared high-temperature superconducting line has obvious advantages when applied to large superconducting power equipment.