The invention discloses a fixing device for an ink-jet printing machine for automobile parts. The fixing device comprises a base. Two stand columns are arranged on the top of the base. The stand columns are correspondingly located on the two sides of the axis of the base. A connecting rod is arranged between the two stand columns. The two ends of the connecting rod are correspondingly connected with the inner sidewalls of the two stand columns. Two sliding blocks are arranged on the connecting rod. The connecting rod is sleeved with the sliding blocks. The sliding blocks can move in the axis direction of the connecting rod. A support cylinder is arranged on the top of each sliding block. A support rod is arranged in each support cylinder. Each support rod can move in the axis direction ofthe corresponding support cylinder. A support plate is arranged on the top of each support rod. Two arc-shaped support frames are arranged on the top of each support plate. The arc-shaped support frames can move in the horizontal direction of the corresponding support plate. Connecting blocks are arranged in the arc-shaped support frames. An adjusting rod is arranged between the connecting blocksof every two arc-shaped support frames. The adjusting rods are connected with the connecting blocks through threads.