polyester fiber having suitable mechanical, physical and chemical properties, constitute a large portion of the fibers used in the textile industry. Advantages such as high strength, excellent resistance to chemical and biological agents, low cost of production and the variety of applications in different industries, these fibers are among the most widely used in clothing and industrial textiles Studies show that laser technology due to cost effective, industrialization and the no production of toxic gases good way to improve the physical and mechanical properties of polyester fiber. Carbon dioxide lasers (IR) wavelength 10.62 micrometers, due to its low price and its availability in the industry have a very broad field, so that this type of laser is the most widely used component of the laser. The study shows that many researchers have used carbon dioxide laser engraved on the fabric, cut and make a pattern on clothing, but the impact of irradiation on mechanical and physical properties of the fibers. In this project, the effect of laser jet on physical and mechanical properties of the polyester fiber was evaluated and the impact of different conditions on the physical and mechanical properties of yarns and fabrics as (strength, elongation at rupture, resistance to tearing, handel, weight variation and non-uniformity in diameter, pilling, double refractive index, infrared spectroscopy and (FTIR) and crystallinity index) was assessed by using physical and mechanical analysis. The results of this study indicate that irradiation by using carbon dioxide laser jet (IR) on polyester fiber caused improvement physical and mechanical properties without changing the properties of the fiber mass. The surface structure of the fibers was studied using SEM. images of SEM showed that the laser irradiation with micro-particles influenced on the fiber surface roughness and surface roughness has effect on contact angle and moisture absorption. Laser irradiation operations improved (pilling, Resistance of tearing, moisture absorption, contact angle and crystallinity index .But the strength of treated yarn and fabric was decreased. The optimization of the irradiation operation parameters, such as output power of the laser beam, irradiation time, the scanning speed of the laser beam on the surface, the diameter of irradiation and have an influence on improvement of treated fiber and fabric properties. Keywords: Laser CO2, polyester, properties, physical and chemical