The invention discloses a technological method for purifying a magnesium melt by utilizing a temperature gradient. The technological method comprises the following steps: adopting a three-section type smelting furnace, taking conventional commercial pure magnesium as a raw material, setting a melting temperature to be 740 DEG C in the presence of protective gas, and melting to obtain the uniformly mixed magnesium melt; then, setting the temperature gradient with a temperature difference of 30-60 DEG C for upper, middle and lower parts of the smelting furnace, and properly increasing cooling velocity of the lower part of the melt by utilizing air cooling to enable the temperature of the lower part of the smelting furnace to quickly reach a set temperature; when confirming that the temperatures of the upper, middle and lower parts of the smelting furnace reach the preset temperature, keeping the temperature and standing for 50-70 minutes; cutting off a power supply of a resistance furnace to enable the melt to be air-cooled and condensed to obtain a purified magnesium ingot. The process is that on the basis of existing magnesium melt standing treatment, other impurity removers are not added and different standing treatment temperature gradients are set only, so that the iron impurity content of the magnesium ingot is remarkably reduced, the quality of the magnesium ingot is remarkably improved, and the purpose of purifying the magnesium melt is achieved. The technological method is good in purifying effect, simple to carry out, low in production cost and easy for realizing industrial production.