The invention provides a detection system and detection method for low-altitude slow small targets. The detection method includes the following steps that: electromagnetic waves are emitted through adetection radar, electromagnetic waves reflected by a target are received, and the point trace and flight trace information of the target is obtained; unmanned aerial vehicle frequency band electromagnetic signals are received through spectrum detection, signal electromagnetic feature information is extracted, and is compared with unmanned aerial vehicle remote control and telemetry signal electromagnetic features in a database, whether the signals are unmanned aerial vehicle signals is judged, unmanned aerial vehicle direction finding information is obtained; the visible light video and infrared video information of the target is obtained through photoelectric detection; broadcast signals emitted from an onboard type ADS-B system are monitored in real time, the point trace and flight trace information and identity information of the cooperative unmanned aerial vehicle target are obtained; all the above information is integrated, so that the comprehensive information including point and flight trace, category, cooperative/non-cooperative identity information and tracking video information of the target can be obtained. Compared with the prior art, the detection system and detectionmethod can realize three-dimensional positioning, speed measurement, category identification and point trace generation of a low-altitude unmanned aerial vehicle target, a monitor the cooperative target in real time so as to obtain a low-altitude flight real-time trend.