Abstract: Magnetic particle indication usually occurred on 1Cr15Ni4Mo3N steel components repaired by laser direct metal deposition technology during magnetic particle testing. In order to determine the position of magnetic particle indication, the designed samples were measured by magnetic particle inspection. The morphology of the magnetic traces and microstructure of the repaired joint were observed and studied to analyze the characterization and forming reason of the magnetic traces. The results indicate that the magnetic particle indications, detected on the 1Cr15Ni4Mo3N steel repaired by laser direct metal deposition technology, are completely coincident with the outer outline of the repaired zone. The morphologies of the repaired zones are able to confirm that the magnetic particle indications are pseudo-magnetic traces. The special magnetic particle indication is mainly attributed to the great difference of austenite content between the 1Cr15Ni4Mo3N steel substrate and its repaired zone.