The present invention discloses a brick, comprising a brick body, which comprises at least one slot position for connecting a column, and a method for using the bricks to build dikes in water, including the following steps: (1) drilling a plurality of pile holes at water bottom; (2) casting concrete into each of the pile holes to form concrete columns; (3) stacking up a number of the bricks along the concrete columns and having them tightly connected to form a wall; (4) filling the clearances between the concrete columns and the bricks with mortar. The bricks and dike building method provided by the present invention are suitable for direct over-water dike building, the construction is fast and the dikes built are firm and stable, have superior waterproof function and can effectively prevent the impact of currents, winds and waves.