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 (121-1) configured to provide a driving force for separating the medicament to be spread from the storage module ; a first pipeline (121-2) configured as a pipeline through which the medicament being separated from the storage module , an end of the first pipeline (121-2) being connected with the outlet of the storage module , and another end of the first pipeline (121-2) being connected with the driving pump body (121-1); and a second pipeline (121-3) configured to guide the medicament to the medicament outlet , an end of the second pipeline (121-3) being connected to the driving pump body (121-1), and another end of the second pipeline (121-3) 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 (121-1) configured to provide a driving force for separating the medicament to be spread from the storage module ; a first pipeline (121-2) configured as a pipeline through which the medicament being separated from the storage module , an end of the first pipeline (121-2) being connected with the outlet of the storage module , and another end of the first pipeline (121-2) being connected with the driving pump body (121-1); and a second pipeline (121-3) configured to guide the medicament to the medicament outlet , an end of the second pipeline (121-3) being connected to the driving pump body (121-1), and another end of the second pipeline (121-3) being in communication with the medicament outlet . <EOS>