The invention discloses a 3D mold overlaying intelligent robot. The 3D mold overlaying intelligent robot comprises two X-axle cross beams; two Y-axle cross beams are mounted between the top surfaces of the two X-axle cross beams, and are driven to move along the X-axle cross beams through respectively independent transmission devices; Z-axle vertical guide rails are respectively mounted on the two Y-axle cross beams, and are driven to move along the Y-axle cross beams through Z-axle transmission devices; a welding head is slidingly mounted on the Z-axle vertical guide rail of one Y-axle cross beam; a welding destressing device is mounted on the Z-axle vertical guide rail of the other Y-axle cross beam, and comprises a high-frequency hammering device and a dust sucking device; and a constant-temperature mold heating device is mounted below the middle of the two X-axle cross beams. The 3D mold overlaying intelligent robot guarantees the temperature in the welding process, improves the welding quality, reduces the influence on the welding precision by higher temperature, adopts the welding destressing device to remove slag to guarantee the flatness after welding, and can be used for repairing a mold and printing a new mold.