The invention discloses a flat glass tempering apparatus, which includes a glass plate heating furnace and a glass plate tempering unit composed of a roller way and an air grid. Between the heating furnace and the tempering unit, a through-type glass plate pre-moulding chamber is arranged, wherein the internal temperature of the pre-moulding chamber is lower than external environmental temperature. When high-temperature softened glass plates pass through the pre-moulding chamber, the pre-moulding chamber pre-cools the glass plates by means of the internal low-temperature environment therein, thereby hardening the glass plates, so that the capability of resisting deformation due to air pressure of the glass plate in the follow-up tempering unit. In the apparatus, by means of addition of the pre-moulding chamber before the tempering unit, the high-temperature softened glass plates are pre-cooled, thereby improving the rigidity of the glass plates and improving the capability of resisting vibration deformation due to the air pressure of the glass plate in the tempering unit, so that the flat tempered glass is improved in waviness.