The mat foundation is generally used in tall building in order to transfer vertical load of columns down to piles. Because of the mat foundation had large dimension, especially the high thickness, the temperature rise of the concrete is concerned. Thermal cracking problem from the temperature difference between surface and centre of the mat foundation concrete has to be prevented. This paper presents a case study of construction technology for mat foundation concrete in tall building. The mat foundation had dimensions of 30.1x34.7 meter with thickness of 2.5 meter to support super structure of tall building which had total height of 146 meter (40 stories), and had sky pool at roof deck. The method statements of concrete work to construct the mat foundation were shown. The large volume of 2,850 m3 of low heat concrete is supplied to cast the mat foundation. The temperature rises of mat foundation concrete were monitored until 7 days of curing with insulation. The results indicated that the low heat concrete containing fly ash generated the highest temperature of 76.4°C. In addition, the temperature difference between surface and centre of the mat foundation concrete were not more than 20°C, within structural specification limited. As a result, the thermal cracking is not occurred in this mat foundation concrete when this method statement of construction is performed.