An I-shaped film repairing technology for an underwater concrete crack comprises the following steps of (1) determining a technical scheme, (2) installing a composite outer wrapping plate, (3) installing an inner wrapping plate on the surface facing water, (4) installing an outer wrapping plate on the surface back onto water, (5) conducting grouting and (6) conducting acceptance inspection. According to the I-shaped film repairing technology for the underwater concrete crack, the defects in the prior art are overcome, the high-difficulty and high-requirement procedures of grooving, chip removal, blocking and the like are reduced, template construction is formed, the construction speed is greatly increased, the construction difficulty is greatly reduced, an anti-permeability system is greatly improved, the anti-permeability effect is greatly improved, and firm connection is further enhanced. Meanwhile, according to the scheme, an elastic formwork and a rigid formwork are combined, rigid blocking materials are replaced, and the impact resistance, corrosion resistance and replaceability of coverings on the surface of the crack are improved. The rainfall influence on a lot of reservoir and port engineering cofferdams is reduced, the complexity of underwater construction is reduced, the concrete crack can be effectively treated at the early stage, and meanwhile maintenance work is easily carried out after treatment.