Steel structure buildings are becoming more and more popular due to their many advantages such as better satisfaction with the flexible architecture, durability, strength, design, low inclusive cost and environmental protection. Steel can also be manufacture with precision and in uniform shapes. Several Attempts are made by the Structural engineers to reduce the cost of steel structures. Due to limitations on maximum allowable deflections, the high strength properties of structural steel cannot always be utilized to best advantage. As a result several new methods have been aimed at increasing the stiffness of steel members without any increase in weight of the steel required. Castellated beam is one of the solutions. A beam with a number of regular openings in its web is called a castellated beam. Castellated beam gain its advantage due to its increased depth of section without any additional weight. Castellated beam has some limitations also; the occurrence of the holes in the web will change the structural performance of the beam from that of plain webbed beams. Stress concentration occurs near the perforations and the shear carrying capacity is reduced. Steel I sections of ISMB 150 is selected and castellated beam is fabricated, such that depth of the castellated beam is 1.5 times more than the original depth. Experiments are carried out by applying two-point loads and deflection of beam is studied and different failure modes are analyzed