The invention discloses an automatic leveling device and method for a horizontal plane of a three-dimensional water tank. The device comprises a water tank fixing plate and a
leveling mechanism; the water tank fixing plate is used for installing the three-dimensional water tank; the
leveling mechanism is arranged at the bottom of the water tank fixing plate; the
leveling mechanism comprises a lower supporting plate, and a first leveling mechanism, a second leveling mechanism and a third leveling mechanism which are mounted on the lower supporting plate; each of the first leveling mechanism andthe second leveling mechanism comprises a round base, a screw rod adjusting mechanism and a screw rod driving mechanism; and the screw rod adjusting mechanism comprises an adjusting gear and a screwrod. The method comprises the following steps of 1, mounting the three-dimensional water tank and carrying out water filling; 2, establishing a space rectangular coordinate
system; 3, measuring a slope of the three-dimensional water tank; 4, judging the mechanical precision; 5, obtaining an inclination angle of the three-dimensional water tank; and 6, leveling the three-dimensional water tank. Theautomatic leveling device and method is reasonable in design, and the three-dimensional water tank can be leveled quickly and accurately, so that the
radiation treatment effect is ensured.