This work studied Al–Al 2 Cu eutectic, which was prepared through unidirectional solidification (1μm/s) with a high magnetic field (10T). The transverse section of the eutectic obtained with the 10T magnetic field showed disorganized and furcated microstructures, as compared with what prepared without the magnetic field. TEM observation suggested that the orientation relationship between Al and Al 2 Cu obtained with the 10T magnetic field did not show significant difference from the 0T counterpart. The [001] Al and the [0 0 1]Al2Cu inclined to the direction of the 10T magnetic field to make the system magnetization energy lowest. A mechanism, which attributes this phenomenon to being the result of coactions from the high magnetic field and the temperature gradient, was presented.