This study aims to analyze the behaviour of hollow core placing in the tension zone of reinforced concrete beams. The hollow was filled with plastic bottle waste. The partial replacement of concrete below the neutral axis by using a different layer of plastic bottles was discussed. The cross-section is filled with plastic bottles, in order to get a lighter structure, reduce the volume of concrete/cement and the reduction of environmental pollution. This study used RC beams with concrete strength of 25 MPa and dimensions of 150 x 350 mm, with 3D16 mm longitudinal reinforcement with the yielding strength of 475 MPa. Four type specimens are tested, consisting of control beam and hollow beams type with the height variation of 600 mm (BR1C), and 1800 mm (BR3C). The length of the hollow for each type was 1760 mm (8 bottles) The results indicated that the flexural capacity of the reinforced concrete beam with hollow-core using plastic bottles was almost same with the normal beam. Moreover, the effect of the height of the hollow core was also insignificant on the flexural capacity, where the beam with higher hollow-core showed similar flexural capacity with the beam having a lower hollow. However, the stiffness of reinforced concrete beam was affected by the height of the hollow core, inherent the higher the hollow core, the smaller the stiffness of the beams.