The invention discloses a dynamic detection system of an overhead line system. The dynamic detection system comprises high pressure data collection portions arranged on the two sides of the roof of a locomotive, a low pressure data collection portion arranged in the middle of the roof of the locomotive, and a data processing portion arranged inside the locomotive. Each high pressure data collection portion comprises a storage battery, a current controller electrically connected with the storage battery, a current transformer, a stagger value detection unit and a hard spot detection unit, wherein the current transformer, the stagger value detection unit and the hard spot detection unit are connected with the current controller. The low pressure data collection portion comprises a visual camera, an infrared camera, a GPS positioning module, a 4G wireless module and an electric arc unit which are connected with the data processing unit. The data processing portion comprises an image processing host, a signal collector and a UPS, wherein the signal collector and the UPS power source are connected with the image processing host. The system can achieve online detection of the overhead line system and a bow net operation state in real time in an all-weather mode and can timely find abnormal defects existing in the overhead line system.