An underwater rapid repair material for marine steel structure comprises: 20 to 50 parts by weight of an alkali activation material, 3 to 12 parts by weight of a fast hardening waterborne polymer curing agent, 2 to 8 parts by weight of a fast hardening waterborne polymer precursor, 30 to 100 parts by weight of an aggregate, 1 to 5 parts by weight of an activator and 3 to 20 parts by weight of a water. The underwater rapid repair material provided by the present invention is not dispersed and segregated in water, with an initial setting time as low as 0.5 hours and a final setting time as low as 1.1 hours, after pouring 3 hours, the compressive strength and flexural strength can reach about 60 MPa and 10 MPa respectively, and has high bonding strength to steel and is not easy to fall off after solidification.