Polypropylene (PP) has been widely used in various industrial fields because of the advantage in high strength, light-weight, and low cost. However, neat PP still have insufficient mechanical properties such as elastic modulus and impact strength. Polymer composite technology, for example, glass fiber reinforced plastics (GFRP) has been admitted being a high performance reinforcement material in improving strength and elastic modulus. There are two types of commercialized GFRP including glass fiber (GF) and glass wool (GW). Although GF is well known in various polymer composites, the processability in the injection molding still need to be improved due to warpage and long cycle-time. In order to solve these problems, GW is one of the alternative materials, because GW has more advantage in aspect ratio and softness. However, fundamental study on PP/GW is still in the lack of progress. For these reasons, this research aims to clarify the fundamental molding characteristics and physical properties of glass wool reinforced plastic. In this research, PP/GW, PP/GF (90/10 and 80/20 wt%) was prepared by single screw extruder machine with 20 rpm-screw speed at 200℃. The specimen was shaped by the injection molding. The results revealed that the shrinkage rates of molded parts is about 1.6, 1.1, 1, 1, and 0.8% for neat PP, PP/GW (90/10 wt%), PP/GW (80/20 wt%), PP/GF (90/10 wt%), and PP/GF (80/20 wt%), respectively. However, warpage increased in order of neat PP, PP / GW, PP / GF. The warpage of PP/GF increased compared with PP/GW since PP / GF has greater anisotropy. The warpage of PP/GF is greater than that of PP/GW since PP/GF has greater anisotropy.　Furthermore, PP/GF is known to hold poor surface smoothness and abrasion resistance property. However, GW is more flexible, therefore, it can be expected that the surface smoothness abrasion resistance property will be improved.