Two way slabs have a lot of usage in many structure systems because of their special behavior and properties. Two way slabs can supply longer spans with a thin thickness in the compare with other structural systems. But they have some special disadvantages in design and serviceability. Large deflections and serviceability problems and weakness against lateral loads are the main of these disadvantages. Slabs have some types based on their conditions. Based on the presence or absence of the beam, slabs divide in to categories: flat slabs and beam-slabs. At this study, the flat slabs are discussed. Because of absence of rigid structural member in the joint of the flat slab and column, all of the applied load should be transferred via the joint of flat slab and column that causes a complicated distribution of stresses in the joint. Presence of some additional applied loads such as moment transfer complicates it more. Punching shear and attempt to prevent it to happen, is a great challenge in the design of flat slabs and is an important Criteria for designers. Sometimes the changes in usage, design and practical errors, concrete damages, steel corrosion, changes in design codes, creation an opening, and some other reasons, implement the strengthening of an existing joint. The strengthening of these joints includes some techniques such as use of stud, steel plates or FRP composites. The main concentration of this thesis is on the use of FRP laminates to increase the punching shear capacity of flat slab joints. For this purpose, nonlinear model of concrete has developed in the finite element application, ANSYS. After calibration of the program and verifying the results of the models of one beam and two flat slab-column joint with experimental results, a model of joint designed for experience of punching shear was modeled in the application. After determination of the effect of efficient parameters on the modeling of joint and achieving a suitable model, FRP laminates added to the model in different arrangements. The effect of different parameters on the joint has been studied. The results shown that in the samples designed for experience of punching shear, the strengthening with FRP laminates do not change the mechanism of failure. The ultimate load of the joint increases by the use of FRP laminates. But the ultimate displacement of the joint will be decrease in the presence of FRP laminates. One way to prevent this disadvantage effect on the ultimate displacement is the use of studs in near the column. The use of studs decreases the undesirable effect of FRP laminates on the ultimate displacement. The results have shown that the use of FRP laminates can increase the ultimate load of the joint up to 80 percent depending on the original properties of the sample and the rehabilitation procedure.