The invention discloses a ship safety alarm device based on a TETRA digital trunking system. The device comprises a hand-held terminal. The hand-held terminal comprises a microprocessor, a TETRA transceiver, a GPS module, a voice processor, keys, a display screen, a loudspeaker, a telephone receiver and a microphone. The TETRA transceiver, the GPS module, the voice processor, the keys, the display screen and the loudspeaker are all connected with the microprocessor. The voice processor is respectively connected with the telephone receiver and the microphone. The invention further discloses a ship safety alarm method based on the TETRA digital trunking system. According to the device and method, on the basis of existing TETRA function services, the functions that an automatic early warning is given for the safe distance between ships and a ship danger shortcut key alarm is given are additionally achieved, the danger that the ships collide with one other is avoided, the rapid help seeking capacity when the ships are in danger is improved, and therefore it is guaranteed that ship sailing is safe.