ملخص البحث رقم (7) باللغة الإنجليزية ABSTRACT The current research aims to identify the most appropriate sewing seam for denim jacket fabrics and to identify the best (sewing seam , stitch length , tensile type) so cotton 100% denim fabrics were used with weave structure twill 2/1 , and some variables : three sewing seams (regular , French , English ) , three stitch length (2,3.5, 5)mm and three tensile type (low, medium, high) with fixation the other factors of the sewing . The research followed the experimental analytical, some laboratory tests were done sewing (tensile strength, elongation, stiffness, appearance, efficiency), the results were analyzed statistically using one- way ANOVA analysis of variance and LSD test for multiple comparisons, the research concluded that the best sample was with the English seam, stitch length 2mm and tensile type medium while the least sample was with the regular seam, stitch length 5mm and tensile type light. The research is great importance in determining the best seams of denim fabrics to reach the highest quality specifications that achieve the functional performance of the final product, and the two researchers recommend the necessity of linking research centers and readymade factories to identify the most important problems facing the denim clothes. Key words: The Functional Performance, denim (jeans) , sewing technique