The invention provides a device and a method for preparing remolded soil with specific water content. The invention is used for preparing the remolded soil with the specific water content in an indoor soil test. The device comprises a motor base, a charging basket and a water injector. The charging basket is arranged on the motor base, the bottom of the charging basket is provided with blades of a rotatable chassis for stirring the soil, the inner wall of the charging basket is provided with an upper humidity sensor, a middle humidity sensor and a lower humidity sensor which are connected with an outer wall humidity indicator, and a nozzle of the water injector is connected with a cover hole opening on the charging basket. Water in the water injector is pressured by a pressuring handle, so that the assembled charging basket is arranged on a rotation shaft of a motor of the motor base, and a power source is switched on, so that a soil sample is stirred. A speed adjusting disc for controlling rotation direction is arranged on the motor, so that the soil sample is stirred and the water injector is used for spraying water, and when the humidity sensors reach to a preset value, the stirring is stopped. The remolded soil with the specific water content is taken out for the indoor test. Compared with the existing method for preparing the remolded soil with the specific water content in the indoor test, the device and method disclosed by the invention are obvious in advantages, automatic to operate, and exact to prepare the water content.