The invention discloses an automatic sewage detection device. The automatic sewage detection device comprises an unmanned boat, a signal base station and a sewage detection base device, wherein a sonar detector, a power turbine group, a sampling window, a discharging hole, a power electrical connector, a water level sensor and a suspension substance detector are arranged on the unmanned board, thesignal base station comprises a signal transceiving device, a positioning device, an information processing device, a loudspeaker and an operation control system, a water pump is arranged in the unmanned boat, an inlet of the water pump is connected with a water hose and a lead block, the water hose penetrates through the sampling window through a guide pipe, a displacement sensor is arranged below the guide pipe, and an outlet of the water pump is connected with a fresh water storage box, a sewage reservation box and a sewage detection base device. By the automatic sewage detection device, sewage detection can be performed in a site in real time, first hand information is conveniently acquired, more accurate data is provided for subsequent research, meanwhile, remote operation is utilized, a worker is prevented from reaching a sewage operation site, the workload is reduced, and the worker is also prevented from being away from a sewage environment.