The present disclosure provides a diffusive gradients in thin films (DGT) probe test device for a sediment core in a lake, including: a sampling tube, where, a settlement limit device is disposed on an outer wall of the sampling tube and a DGT probe and a multi-parameter water-quality detection electrode are installed within the sampling tube; a movable mudguard device comprising a connecting rod and a mudguard, where, the connecting rod rotates around a rotating shaft to drive the mudguard to move from a position where an opening at the lower end of the sampling tube is sealed to a side of the sampling tube; a position-limit mechanism removably installed outside the sampling tube; a hammering device located above the sampling tube and fixedly connected to the sampling tube; and a floating ball located above the hammering device and connected to the hammering device via a first pull rope.