In this study, the effect of back rest roller position on cotton plain woven fabric properties on Picanol air jet loom study was conducted at Bahir Dar textile Share Company where the temperature and relative humidity were an average of 26 c0 and 65% respectively. For this purpose, the yarn properties taken were cotton yarn 20 Ne for both warp and weft. Five different back rest roller positions were taken and selected properties of fabric such as fabric density, crimp, breaking strength and extension were tested for each. The end breakage and time taken to repair a single yarn warp break were also studied, and then the finally tested data was analyzed. The results showed that warp breaks were decreasing at back rest roller position between 3-4cm and 3-2cm height and depth respectively. The lower end breakage which is 8 was obtained at back rest roller position at 4 cm height and 2 cm depth at which the minimum end break was achieved. Back rest roller above 4 cm and below 3cm height and above 3cm and below 2 cm depth, warp break starts increase. As an increase the back rest depth, the warp density decrease, decreasing breaking strength in warp direction, decrease elongation in the weft direction and increase elongation in the warp direction and with arise in the back rest height the warp density increase, increasing breaking strength in the warp direction, elongation in the weft direction increase, elongation in the warp direction and warp crimp decrease and weft crimp increase. Also the vertical and horizontal position of the back rest roller have no influence on the weft yarn density of fabric and on breaking strength of fabric in weft direction. Generally it can conclude that the back rest roller position has a significant effect on efficiency of the loom and consistence in fabrics properties.