The invention discloses a floating ball liquid level device for measuring a concrete liquid level of a pouring pile foundation and a using method thereof. The device comprises a floating ball, a measuring device, a displacement sensor, a traction rope, a fixed support, and a shield; the measuring device comprises a spring deformation instrument, and the spring deformation instrument is located inside the hollow portion interior of the floating ball; the floating ball is a spherical body, the upper hemisphere is a hollow portion, and the lower hemisphere is a solid portion; the shield is weldedto the fixed support; the floating ball is connected to the fixed support by the traction rope and disposed inside the shield; the floating ball liquid level device is integrally connected to a steelbar cage by welding or binding, which can control the height of the concrete liquid level. The device cooperates with the electronic components to monitor the slight deformation of the spring througha mechanical unit, and more precisely controls the liquid level, so that the device is safe and reliable, is easy to operate, and can effectively control over-pouring of a bored pile; and the floating ball of the present invention can distinguish between a concrete layer and the floating grout layer, and effectively control the concrete liquid level.