The invention discloses a device and a method for acquiring traffic information. A plurality of node devices for traffic information acquisition based on video are arranged on one side of a road one by one, and are used for acquiring the information of two-way traffic flow on the road. The adjacent node devices communicate with each other in a wireless mode so as to form a wireless sensor network. Visual fields of adjacent node devices have a covered overlap region used for providing the adjacent node devices with cooperation time and space. Through the traffic information synthesis of the adjacent node devices, a lowest-reaches node obtains the traffic information in a whole range. The node devices communicate through a Zigbee protocol, and the synthesis of overall information from the traffic information acquired by the node devices is realized through the cooperation of the adjacent node devices. The acquired traffic information comprises road flow rate, occupancy, average velocityand motion tracks of vehicles. The invention has the characteristics of flexible network structure, as well as the wide range and high real-time property of the acquired traffic information.