The invention discloses a carrier rocket storage tank bottom welded seam X-ray digital imaging detection system comprising a tooling, a dislodgement machine, a first robot, a second robot and a total control unit; a storage tank is fixed by the tooling; the dislodgement machine makes the tooling and the storage tank perform overturning and rotary motion; the first robot and the second robot are respectively arranged at the front side and the reverse side of a welded seam of the storage tank bottom, the first robot is clamped with an X-ray machine, the second robot is clamped with a digital detector, and the total control unit is in communication connection with the dislodgement machine, the first robot, the second robot, the X-ray machine and the digital detector. The invention also discloses a welded seam X-ray digital imaging detection method. The device and the method achieve carrier rocket storage tank bottom welded seam X-ray digital imaging detection, improve the detection efficiency, reduce cost of X-ray detection films, flushing drug liquids, developing machines, darkrooms and the like, and reduce pollution of the films and the flushing drug liquids on the environment and harm of the films and the flushing drug liquids on personnel body health.