Plastic waste is one of the biggest problems that occur not only in the world but also in Indonesia. Therefore, the need for plastic waste management so the problem can be solved. In this research, thermoplastic-based composites are made using LDPE plastic waste, styrofoam and melamine which are then applied as construction materials. In this study used 10 variations of composition. The highest of compressive strength by specimen 4 (with the addition of styrofoam) of 13.72 MPa