The present work performs mechanical buckling analyses and experimental investigation on square plates with central cutout with (circular and elliptical) shape and with different size under uniaxial compressive loading, clamped from the loaded sides and free from others. The plates were mostly used in aircraft structures, rocket and automobiles is aluminum alloy (Al-2024 T3) because it has a high strength to weight ratio. The determination of critical buckling load of metallic plate is an important factor in determining the structural stability, which consider the best examination for buckling behavior. Experimental investigation was carried out on square plates by using strain gages. The experimental results for buckling load were compared with analytical results by using finite element structure analysis technique (F.E.M) i.e. using (ANSYS) software. Results have been presented that the square plates with circular and elliptical cutouts decrease in buckling strengths as the cutout sizes were increased.