The article describes the tests of high temperatures resistances of glass reinforced cement plates. The first part is focused on determining the values of strength in bending for samples subjected to annealing at temperatures 200, 300, 400 and 500 °C and endurance at the highest temperature level was for 24 hours. The results are compared with values obtained for the reference samples. The bending strength was performed as tree-point bending test. Furthermore, the thermal dilatometric analysis was performed in the temperatures till 540 °C in the second part and GT-DTA analysis explaining chemical changes at height temperature was conducted.