The invention provides an Mg-Gd-Y-Zr magnesium alloy refining flux and a production method thereof. The chemical components of the flux are mixed according to the following mass percentages: potassium chloride of ranging from 30 to 50 percent, barium chloride of ranging from 5 to 20 percent, sodium chloride of ranging from 2 to 10 percent, calcium chloride of ranging from 10 to 20 percent, calcium fluoride of ranging from 2 to 8 percent, cryolite of ranging from 1 to 5 percent, gadolinium compound of ranging from 3 to 8 percent, yttrium compound of ranging from 3 to 8 percent, and zirconium compound of ranging from 2 to 8 percent, wherein, the gadolinium compound is gadolinium chloride, gadolinium carbonate or gadolinium fluoride, the yttrium compound is yttrium chloride, yttrium carbonate or yttrium fluoride, the zirconium compound is zirconium tetrachloride or potassium zirconium fluoride. The flux has good melting point, viscosity, wettability and the slag removing performance which is improved greatly. Because the flux does not contain magnesium chloride or react with the lanthanon such as gadolinium and yttrium, the chemical reaction loss of the lanthanon in the refining process is not caused, thereby being particularly suitable for the refining purifying process of the Mg-Gd-Y-Zr magnesium alloy and improving the refining effect of the magnesium fused mass.