Disclosed are a nano-patterned system and a magnetic-field applying device thereof. The nano-patterned system comprises a vacuum chamber, a sample stage and a magnetic-field applying device. The magnetic-field applying device comprises a power supply, a magnetic-feld generation device and a pair of magnetic poles. The magnetic-field generation device comprises a coil and a magnetic conductive soft iron core. The power supply is connected to the coil, and the coil is wound on the magnetic conductive soft iron core to generate a magnetic field. The magnetic conductive soft iron core is of a semi-closed frame structure, and the magnetic poles are respectively arranged at the two ends of the semi-closed frame structure. The sample stage is arranged inside a vacuum chamber of the nano-patterned system. The magnetic poles are oppositely arranged inside the vacuum chamber relative to the sample stage. The coil and the magnetic conductive soft iron core are arranged outside the vacuum chamber. The magnetic conductive
