The invention discloses a liquid nitrogen filling device and a liquid nitrogen filling system. The liquid nitrogen filling device comprises a filler (1), a liquid nitrogen tank (2), a liquid feeding pipe (3), a liquid discharging pipe (4), an electromagnetic pump system (18), an air feeding device and a safety device, wherein the liquid discharging pipe (4) and the liquid feeding pipe (3) as well as the filler (1) are of a split type structure, and are in movable connection state, a filter device (6) is arranged at one end of the liquid feeding pipe (3), a rapid joint (7) is arranged at one end of the liquid discharging pipe (4), a high-temperature superconduction radio-frequency coil (8) is arranged at one end of the rapid joint (7), a control device is arranged at the other end of the high-temperature superconduction radio-frequency coil (8), an automatic air bleeding device (19) is arranged at one end of the control device, and the filler (1) is connected with the liquid nitrogen tank (2) by a sealing-fixing device. Due to the adoption of the structure, the high-temperature superconduction radio-frequency coil can be filled with liquid automatically, the safety of operators is ensured, the labor intensity of workers is alleviated, the purpose of long-time continuous work is realized, and liquid nitrogen filling device can be compatible with a magnetic resonance system.