The main objective of this paper is to reach to the more advanced and suitable finishing treatments on the dimensional properties and the regularity of weft-knitted fabrics. We also utilized image processing technique based on Radon transformation analysis to consider the twofold effect of different relaxation methods on stitches shape and dimensional stability of two popular weft-knitted structures (Plain and Interlock). We applied various mechanical, chemical and complex (mechanical-chemical) relaxation regimes on knitted fabrics to decrease fabric internal stress and make stitch shape closer to an ideal shape. The rhythm of stitch shape enhancement during various relaxation processes was evaluated by measuring the deviation of stitches direction angle to an ideal state on weft-knitted fabrics produced from different yarn types. The index of fabric regularity was obtained from the deviation of stitches from the original direction of ideal regular fabric after any relaxation process by both conventional and image processing methods. The average of fabric constant dimensional parameters ( K s and U s ) after ultrasonic-chemical relaxation treatment is higher than values reported by pervious workers. Also fabric regularity index after this process is better than other relaxation method. Therefore we propose the ultrasonic-chemical relaxation treatment as a new relaxation method that it is more effective on knitted-fabrics regularity and dimensional stability during usage. Also the results still supported the major effect of yarn type and fabric structure on fabric irregularity