A high-density magnetic memory device includes: a heavy metal strip or an antiferromagnet strip with a thickness of 0-20 nm, and a plurality of magnetic tunnel junctions manufactured thereon, wherein each of the magnetic tunnel junctions represents a memory bit, which from bottom to top comprises a first ferromagnetic metal with a thickness of 0-3 nm, an oxide with a thickness of 0-2 nm, a second ferromagnetic metal with a thickness of 0-3 nm, a synthetic antiferromagnetic layer with a thickness of 10-20 nm and a No. X top electrode with a thickness of 10-200 nm, wherein an X value is a serial number of the memory bit; two ends of the heavy metal strip or the antiferromagnet strip are respectively plated with a first bottom electrode and a second bottom electrode. The write operation for the memory device of the present invention is accomplished by applying unidirectional write currents.