The invention discloses a radar scanning device capable of monitoring the change of the charge level of a blast furnace in real time. The radar scanning device is arranged at a proper position, so that the real-time property and the authenticity of charge level imaging can be ensured. A radar antenna stretches into the interior of the blast furnace; the rotation of the antenna is controlled through a mechanically-designed transmission device; the half charge level of the blast furnace is scanned by considering an optimal visual angle range and an optimal distance measurement range at a selected position.