The invention provides a water tank structure for a load test, a test device and a test method. The water tank structure comprises a plurality of water tanks which are uniformly distributed layer by layer and stacked on a support, adjacent water tanks of each layer are communicated through a connecting water pipe, a top surface of each water tank is provided with a water inlet, the bottom surfaceof each water tank is provided with a water outlet, the water inlet is connected with a water pump through a detachable water inlet pipe, and a detachable sealing cover is installed at a water outletend. According to the wate tank structure for the load test and the load test method provided by the invention, the water tank is used as a loading device for the load test, a corresponding number ofwater tanks are assembled according to the load requirement, water is injected into the water tank during loading, and water in the water tank is discharged during unloading, so that one-time water filling and one-time water discharging are realized; the problems that time and labor are wasted and transportation is inconvenient due to transportation and stacking of concrete blocks or sand bags aresolved, meanwhile, the water tanks are safe to stack, water filling and water discharging are rapid, repeated utilization can be achieved, and transportation, loading and unloading are more convenient and faster.