The main objective of this study is strengthening of flat slabs in punching shear with a new model. For this purpose 15 numerical samples include a control and 14 strengthened defined and nonlinearly analyzed up to failure. The strengthening method is new method of grooving in two orthogonal direction (x and y axes of slab plan) and then mounting the external bars (sticking) in one direction and FRP in EBROG (externally bonded reinforcement on groove) method in another direction. The results showed the great efficiency of the method so that the punching shear capacity of strengthened samples increased between 28 and 62% compare to control one. Also the mode of failure changed in strengthened specimens from shear to flexure–shear and the punching critical area was broader and developed from the loading point. In the grooving method the sticking bars yielded in all specimens and the FRP tensile strain was closer to rupture strain compared to EBR.