The invention provides a plane position control method for the sinking and setting of a steel buoyant box in a shipbuilding base so as to solve the shortcomings of low locating precision, inaccuracy, complex procedures and the consumption of a large amount of time and manpower and materials during sinking and setting the existing steel buoyant box. The method comprises the following steps: 1. a plurality of limiting piers are arranged at the sinking and setting position of the steel buoyant box; 2. the steel buoyant box is leveled; 3. the steel buoyant box is fixed by a bollard and a windlass which are arranged on the limiting piers, and the steel buoyant box is hauled to a pre-sinking posting under the hauling of a tug boat; and 4. water is irrigated to the steel buoyant box by a water inlet valve arranged on the steel buoyant box so as to position the steel buoyant box among all the limiting piers to gradually reach the sinking and setting position. In the plane position control method for the sinking and setting of the steel buoyant box, the plane positioning of the sinking and setting of the steel buoyant box is controlled by relying on the reference substance, namely, the limiting piers, and after the position of the steel buoyant box is precisely locked, the water irrigation sinking is reliably guaranteed.