The invention discloses a parking space detection device and detection method based on an NB-IoT technology. The device comprises an RFID antenna module used for detecting the electronic tag, an RFIDcard reader module used for adjusting the power of the RFID antenna module so as to control the identification range of the RFID antenna module, identifying the parking space and the vehicle information, a geomagnetic sensor module used for detecting whether a vehicle enters or leaves a parking space or not, a single-chip microcomputer used for storing the data information and controlling the NB-IoT module to perform data transmission, and an NB-IoT module used for sending the data information outputted by the single-chip microcomputer to the cloud platform. According to the invention, the RFID card reader module is matched with the geomagnetic sensor module, so that the vehicle identification rate is improved; by adopting the RFID circularly polarized antenna, the antenna identification range is enlarged, the interference of the metal chassis of the automobile on signal transmission can be effectively overcome, the electronic tag is further effectively detected, meanwhile, the identification range of the antenna is controlled by adjusting the transmitting power of the card reader, and the problem of mutual interference among parking spaces in the parking process is effectively solved.