The invention provides a lithium aluminosilicate flat float glass with a high thermal stability which can be chemically and thermally tempered and is suitable for economical and environmentally friendly production. The lithium aluminosilicate flat float glass which can be chemically and thermally tempered, is refined without using a standard refining agent such as arsenic oxide and/or antimony oxide and has excellent thermal stability is constituted so as to contain 2.5-6.0 wt.% Li2O, 0<4 wt.% in total of Na2O+K2O, 0-4 wt.% B2O3, 15-30 wt.% Al2O3, 55-75 wt.% SiO2and <2 wt.% in total of TiO2+ZrO2(the undesirable crystallization of [beta]-quartz and/or keatite solid solution is prevented) as main components per the weight of the total compositions.