An elasto-plastic theoretical analysis of stresses around a square perforated isotropic plate is Studied. The boundary of the plastic stress field around the conformally mapped square holes is obtained by using Savin's complex elastic equations. ANSYS (R) Finite Element Code is Used to find out numerical solutions. The elasto-plastic theoretical and FE solutions are compared for isotropic plates, with rounded corner square openings. Both solution results are in good agreement with each other.