Slope instabilities have occurred in several improper landfills and illegal dumping sites. To investigate the shearing response of solid waste materials, it is important to consider in the stability of dumping site and landfill design. In this study, the shearing responses and shear strengths were investigated by newly developed direct shear test apparatus on four waste grounds that consist of different composition ratios of waste materials. The in-situ experimental results indicated that the shearing responses of waste materials were affected by the existence of fibrous materials. In addition, it could be seen that the shearing responses and shear strengths of various waste materials could be evaluated by focusing on fibrous materials composition. It was noticeably found that the strength characteristics of waste materials was controlled by cohesive rather than internal friction with increasing more than 15% of fibrous materials.