The invention relates to the field of immersed tube tunnels, and discloses an immersed tube tunnel construction monitoring system. The immersed tube tunnel construction monitoring system is characterized in that adjacent tube sections of an immersed tube tunnel are provided with first test sensors used for testing the opening-closing degree between the test tube sections, a second test sensor used for monitoring relative displacement changes between the tube sections in the horizontal direction and third test sensors used for monitoring differential displacement between the tube sections in the vertical direction; the adjacent sections are provided with fourth test sensors therebetween used for measuring the opening-closing degree of a gap between the sections; an end sealing door is provided with stress sensors used for testing the maximum bearing stress and fifth test sensors used for testing maximum deformation conditions; and the adjacent tube sections are provided with sixth test sensors used for monitoring settlement changes of the tube sections, seventh test sensors used for monitoring displacement changes of the tube sections and temperature sensors used for monitoring temperature changes in the immersed tube. The invention further provides a construction technology. The immersed tube tunnel construction monitoring system and the construction technology thereof are comprehensive in monitoring, and capable of ensuring monitoring data to be reliable, timely and effective.