Cotton is the natural textile fiber used most popular in the world to produce yarns, threads, apparel, home furnishings, and other industrial products. Yarn quality is largely influenced by raw cotton materials and spinning technology, dependent on demand quality cotton yarn can be produced by some spinning technologies, but most commonly ring spinning and Open-End spinning technology. The article presents the results of research on tensile strength and break elongation of 3 types of 100% cotton yarns Ne10/1, Ne16/1 and Ne20/1 produced by open-end spinning at Eight March Textile Company Limited and Hoang Thi Loan Company. Tensile strength and break elongation are determined by ISO 2062:2009 standard on TENSILON instrument. The results indicate that the higher yarn’s count density is, the smaller its tensile strength is. Tensile strength of 3 types produced by Eight March Textile Company Limited is much more higher than that of 3 types produced by Hoang Thi Loan company. Yarn break elongation slightly reduces incase yarn’s count density increases. Break elongation of 3 types produced by Eight March Textile Company Limited is more higher than that of 3 types produced by Hoang Thi Loan company.

Keywords: Cotton yarn, tensile strength, break elongation.