Abstract：Abstract：In water-conveying tunnel of permanent shiplock of Three Gorges Project，some cracks are found in early phase cast concrete lining. These cracks，existing in the middle of a tunnel section，and transverse direction，seriously effect the quality and life span. So，field experiment on concrete lining temperature field of tunnel sections NY9 and NY10 of north extension，where temperature-controlled concrete and no special temperature controlled concrete are cast，respectively，is conducted. Experimental results show：(1) the highest temperature of lining caused by hydration heat can reach above 50 ℃；and (2) both the temperature rise and the temperature drop are quickly. The concrete lining temperature begins to drop within 3 days with large drop scope. Because of the thin structure and strong constraint of surrounding rock，lower tensile strength of concrete，etc.，early stage cracks occurred. The reason that cracks are developed during construction periods is analysed；and the importance of temperature controlling to prevent cracks in tunnel lining during construction periods is pointed out. Some feasible measures and proposals are put forward. These measures and proposals，adopted by construction units are proved to be effective and economical.
