A magnetic tunnel junction device includes a pinned magnetic layer, a free magnetic layer embodied as a synthetic antiferromagnetic device, and a nonmagnetic barrier layer sandwiched between the pinned magnetic layer and the free magnetic layer. The free magnetic layer includes a first ferromagnetic layer, a second ferromagnetic layer and a nonmagnetic spacing layer sandwiched between them; and can transform from the antiferromagnetic state to the ferromagnetic state regulated by electric field. Under the coaction of the electric field and the current, the ferromagnetic layer close to the barrier layer of the magnetic tunnel junction is switched to write in data. Also, a magnetic random access memory based on a synthetic antiferromagnetic free layer can write in data under the coaction of the electric field and the current, and has advantages such as simple structure, low power consumption, rapid speed, radiation resistant, and non-volatility.