The invention relates to a method utilizing solder for assisting in measurement of the weld nugget zone temperature in a friction stir welding process and solves a problem that the weld nugget zone temperature of a friction stir welding temperature field in a practical measurement process can not be measured. The method comprises steps that 1, various types of Zn-Al solder with aluminum element contents from low to high are prepared, each type of Zn-Al solder is made into Zn-Al solder sheets; 2, the Zn-Al solder sheets with different contents are pasted on butt joint or overlapping interfaces; 3, a friction stir welding machine starts, a stirring head is welded in a welding direction; and 4, after welding, the solder is extracted from the pasting position of each type of the Zn-Al solder sheets for the friction stir welding weld, weld cross sections are observed through a metallographic microscope, if no solder solid is observed at a weld nugget zone, only a few of solder solid fragments are scattered at a thermo-mechanically affected zone, the solder is determined to just melt in the friction stir welding process, and the melting point of the solder is equal to the temperature of the weld nugget zone in the friction stir welding process. The method is used for measuring the temperature of the weld nugget zone in the friction stir welding process.