Abstract: In order to discuss the relationship between linear density of yarn and weft insertion flying state on Dornier air-jet loom, and provide technological base to optimize the process of weft insertion , this paper used Dornier AWV8/S air-jet looms as the experimental platform and the actual weft insertion flying state of Weft slot in the reed was recorded through a high-speed camera system. Then the professional image analysis software- Image pro-plus 6.20 was used to analyse the images of the weft insertion flying state. Average speed, acceleration and vertical wave distance of wefts with different linear density were obtained. The results show that the velocity and acceleration of the yarn with the same material texture increase with the increasing of yarn linear density under the same weft insertion condition. And the linear density of yarn is greater，the flight state of the yarn is more stable. Besides, the weft possessed high flight speed and small fluctuations under the 10tex cotton yarn condition. So this air-jet loom has good motion state in such situation.