The invention provides an automatic box turnover manipulator. The automatic box turnover manipulator comprises a first arm, a second arm, a third arm, a first suction cup and a second suction cup. The manipulator grabs a box through the first suction cup, then automatically rotates to turn over the box and transfers the box to the second suction cup on the upper portion. After switching is completed, the first suction cup rotates horizontally to make room, and the second suction cup descends to put the turnover box down. In this way, general grabbing and stacking functions are achieved through one manipulator, and the turnover function after grabbing can also be achieved. The invention further provided with an online box turnover device. The online box turnover device comprises the automatic box turnover manipulator, a frame body, a front-back advancing mechanism and a left-right advancing mechanism. The online box turnover device has more degrees of freedom and completely meets the requirements for online grabbing, stacking and box turnover on irradiation production lines, so that the automation degree of the production lines is greatly improved, a large amount of manual labor is reduced, and the production efficiency is improved.