Abstract: For concrete structures in cold regions， surface insulation measures are often used to protect them from cracks. Based on the theoretical analysis of a formula proposed by Academician Zhu Bo fang， taking the Liulingou aqueduct of the Gansu Tao diversion project as an example， temperature variation and thermal stress are calculated under conditions without heat insulting and with 3 cm and 5 cm polyurethane insulation board. Moreover， the superficial effects of different thickness insulation layers are analyzed in this paper. The analysis results show that the temperature of box aqueduct decreases quickly along with a greater thermal stress during the winter， so the insulation materials with suitable thickness are chosen to reduce the temperature variation and thermal stress in the body surface and corners of the aqueduct， and cracking will be avoided, which may affect the integrity and stability of the aqueduct structure.