A device for in-water automatic spreading configured to spread a medicament in a water body, comprising: a storage module configured to store a medicament to be spread; a driving module configured to drive the medicament to be separated from the storage module, the driving module being connected with the storage module; a medicament outlet configured as an outlet for the medicament to be spread to enter a liquid after being separated from the storage module; a walking module configured to drive the device to move in the water body according to a walking route; and a control module configured to control the driving module and the walking module, the control module being connected with the driving module and the walking module.; characterized in that the driving module comprises a driving pump, configured to drive the medicament to be separated from the storage module; an end of the driving pump being connected with an outlet of the storage module, and another end of the driving pump being connected to the medicament outlet; a driving pump body configured to provide a driving force for separating the medicament to be spread from the storage module; a first pipeline configured as a pipeline through which the medicament being separated from the storage module, an end of the first pipeline being connected with the outlet of the storage module, and another end of the first pipeline being connected with the driving pump body; and a second pipeline configured to guide the medicament to the medicament outlet, an end of the second pipeline being connected to the driving pump body, and another end of the second pipeline being in communication with the medicament outlet. a storage module configured to store a medicament to be spread; a driving module configured to drive the medicament to be separated from the storage module, the driving module being connected with the storage module; a medicament outlet configured as an outlet for the medicament to be spread to enter a liquid after being separated from the storage module; a walking module configured to drive the device to move in the water body according to a walking route; and a control module configured to control the driving module and the walking module, the control module being connected with the driving module and the walking module.; characterized in that the driving module comprises a driving pump, configured to drive the medicament to be separated from the storage module; an end of the driving pump being connected with an outlet of the storage module, and another end of the driving pump being connected to the medicament outlet; a driving pump body configured to provide a driving force for separating the medicament to be spread from the storage module; a first pipeline configured as a pipeline through which the medicament being separated from the storage module, an end of the first pipeline being connected with the outlet of the storage module, and another end of the first pipeline being connected with the driving pump body; and a second pipeline configured to guide the medicament to the medicament outlet, an end of the second pipeline being connected to the driving pump body, and another end of the second pipeline being in communication with the medicament outlet.