A real-time spatial magnetic positioning device, a radiographic imaging system and a magnetic positioning method is provided. The radiographic imaging system comprises a radiation source, a collimator, a flat panel detector, and a real-time spatial magnetic positioning device, wherein the magnetic positioning device comprises a processor, a magnetic field generating device and a magnetic sensor array; the magnetic field generating device is arranged coaxially with the collimator, a plurality of sensors of the magnetic sensor array is distributed on the flat panel detector; the magnetic field generating device is configured to generate an alternating magnetic field, the magnetic sensors are capable of independently detecting magnetic induction intensity in real time, and sending real-time detected data to the processor, and the processor determines a position relationship between the collimator and the flat panel detector according to the data detected by respective magnetic sensors in real time.