The invention discloses white gold alloy for high-temperature enamelled jewellery and a preparation method of the white gold alloy. The white gold alloy is prepared from, by weight, 75.0%-75.5% of gold, 7.0%-8.0% of nickel, 3.0%-4.0% of silver, 9.5%-10.5% of copper, 3.0%-3.5% of zinc, 0.3%-0.8% of palladium, 0.01%-0.03% of silicon, 0.008%-0.02% of scandium and other inevitable impurities. The preparation method of the white gold alloy comprises the steps that 1, raw materials are smelted under the protective atmosphere; 2, after all the materials are melted down, the temperature of molten metal is adjusted, and an ingot casting is obtained through casting; and 3, the ingot casting is rolled and then annealed. The color of the white gold alloy meets the requirement for the color index of K white gold well, and excellent vulcanization color change resistance is achieved; excellent high-temperature oxidation resistance is achieved, high-temperature firing can be borne better, and a transparent enameled layer obtained through firing has good transparency; the expansion factor is close to the heat expansion factor of common high-temperature glaze for gold; and the requirement of inlaid jewellery can be met well, the white gold alloy is fine in grain, and a highly-polished surface can be obtained.