A liquid detection device and a liquid detection system are provided for detecting whether there is abnormal liquid on the surface to be detected. The liquid detection system can be used in specific working areas. A first electrode and a second electrode are used. The first electrode and the second electrode are mounted on the housing. A measuring circuit is installed inside the housing. The measuring circuit measures the impedance value between the first electrode and the second electrode, to distinguish whether there is abnormal liquid or not. The liquid detection system includes a plurality of liquid detection devices and a controller. The controller is responsible for collecting the measurement results of the plurality of liquid detection devices and performing corresponding operations.