Abstarct: The purpose of this thesis is to present a new models baxsed on the regression analysis for estimating stress concentration factor of orthotropic plates with different cutouts baxsed on the mechanical properties of the material, the radius of the curvature of cutout and the angle of rotation of the cutout. Infinite plate under uniaxial tensile load and cutout is located in the center of the plate. The explicit relationship that has the ability to estimate the stress concentration coefficient in different cutout plates, in addition to ease in the use and abandonment of the hard and complex process of analytical solution, it can be applied using the effective modulus method or Boltzmann's superposition principle also calculates the stresses of viscoelastic cutouts. in this research, at first, using different values of the mechanical properties of the composite plates, was calculated stress concentration factor employing an analytical solution baxsed on the complex variable method. Using MLR, was presented an explicit mathematical relation for different cutouts with the purpose of estimating stress concentration factor in terms of mechanical properties. The results showed that the regression model was able to predict environmental stress with a maximum error of 1% for circular, elliptic, triangular and quasi-square cutouts. The effects of parameters such as radius of curvature of cutouts and angle of rotation of the cutout have been investigated as effective parameters on stress distribution. By choosing these parameters correctly, you can reduce the tension caused by cutouts and create an optimal design. The evaluation of the models by k-fold cross validation and comparison with the results obtained from other studies show that the proposed model is very reliable with reliable accuracy. Using the regression models presented in this thesis is very simple and practical.