The invention discloses a device for detection of the carbon dioxide content in urban air, which comprises an air intake pipe, a ventilation pipe, a detection pipe, a carbon dioxide sensor, an air pump and an air outlet pipe. Dozens or hundreds of carbon dioxide monitoring points are arranged in an urban area for detection of carbon dioxide, a monitoring network is formed via coupling through telecommunication lines, and detection data of each monitoring point are summarized to a master monitoring station for analysis and treatment. The carbon dioxide detection device is vertically arranged on the outer wall of a high-rise building, air at different heights is collected through a plurality of air intake pipes, the collected air is delivered to the detection pipe through the ventilation pipe and the air pump, the content of carbon dioxide in the air is detected by the carbon dioxide sensor in the detection pipe, and the automated control and the storage, processing, display and transmission of testing data are carried out by the detector for the carbon dioxide content in the urban air. The device has the advantages of large measuring range, high accuracy, long service life, simple structure, automatic control, easiness in installation, synchronous detection, internetworking transmission, reliability in operation, real-time data display, low manufacturing cost and the like.