The principle of tacking stitching of lockstitch sewing machine was analyzed,pointing out that whether the tacking stitching is in good order or not lies in how to control the tacking relay.

• 对工业平缝机回缝线迹的产生原理进行分析,提出回缝线迹整齐与否的关键技术是对倒缝继电器的控制。