The invention relates to a processing technology of high-flatness tempered glass. The processing technology comprises the following steps of firstly, gradually heating plate glass to 180 DEG C within 200 to 240s; then, heating the glass by phases, namely heating to 260 to 300 DEG C at the speed of 8 to 10 DEG C/min, heating to 380 to 420 DEG C at the speed of 12 to 14 DEG C/min, and heating to 600 to 620 DEG C at the speed of 42 to 45 DEG C/min; quickly putting the glass into an air grid to quickly cool, and cooling the glass to 340 DEG C within 12 to 14s; then, heating the cooled glass to 480 to 520 DEG C within 20 to 22min, and maintaining the temperature for 20 to 30min; naturally cooling, immersing by a sodium sulfite solution, cleaning, and drying, so as to obtain the tempered glass. The processing technology has the advantages that by controlling the heating and cooling processes of the glass, the warp of the tempered glass due to sudden larger temperature difference is avoided; while the production efficiency is guaranteed, the raw piece of the glass is uniformly heated, the overall deformation without torsion is ensured, and the flatness and strength of a tempered glass product are guaranteed.