The utility model provides a structure of grout template under water that column body cross section increaseed, include: template bottom surface basis, the single section steel form sets up around existing cylinder, pieces the single section steel form in order to realize that heavy the putting of merogenesis is assembled under water by 2 half of single section steel forms, gyro wheel slideway structure installs on existing cylinder for realize heavy direction, the support and spacing of putting in aquatic of single section steel form, fine control location structure, install around the single section steel form and inside, toper guide structure is located the top surface flange board and the bottom surface flange board of single section steel form, the rubber strip is only starched to the bottom, is located the bottom surface of coxopodite single section steel form. The utility model discloses can satisfy the applied environment that there is the water upper cylinder body cross -section increasing of overlay structures such as bridge floor or wharf surface at the cylinder top, make difficult structure of grout template under water of construction and construction side method become and easily operate, degree of automation is high, and the quality is reliable, reduces be under construction risk and cost, improves work efficiency.