Abstract: The growth of low heat Portland cement dam concrete strength at early stage is slower than moderate heat Portland cement concrete. It causes certain great differences between these two kinds of concrete in construction technology, construction schedule, temperature measure, their effect, etc. Studies on key construction technologies of this low heat concrete were carried out for dam blocks 30 and 31 of Xiluodu arch dam in June 2013 to analyze the feasibility of its application to ultra high arch dams. Compared with moderate heat cement concrete, the green cutting schedule of low heat cement concrete had delayed 16-20 h and its formwork removal schedule had delayed about 24h, but this did not influence the dam construction schedule since the concreting intermission time of dam concrete is usually around 7 - 10 d. And its highest temperature in the dam blocks was 4.6 ℃ lower and its temperature rise after joint grouting was 1.2 ℃ lower in basically the same conditions of placement temperature, spacing between cooling pipes, and temperature and flow rate of cooling water. When other conditions were the same, low heat cement concrete had a peak stream-wise stress of 19% - 65% lower and its safety factors of crack resistance were generally improved, all reaching a level above 2.0. The transverse joints of a low heat cement concrete dam block can be opened and the required amount of joint grouting is close to that of a moderate heat cement concrete dam block. Up to now, no crack has been found yet in the observed two dam blocks of low heat cement concrete.