The work aims to prepare a new type of composites by utilizing natural degradable polymer to replace part of polypropylene (PP). Polypropylene was used as the matrix of the composites. Konjac glucomannan (KGM) and calcium carbonate (CaCO3) were added to the matrix, and the pellets were mixed and extruded through a desktop extruder in a certain ratio. Then the semi-finished pellets were prepared into PP/KGM/CaCO3 composites by injection molding with an injection machine. Finally, the effects of KGM and CaCO3 on the impact properties and tensile properties of PP/KGM/CaCO3 composites were investigated. Through the one-factor experiment, it could be seen that the mechanical properties of PP/KGM/CaCO3 composites were optimal when the addition of KGM was 10% and CaCO3 was 5%. It is concluded that the composite have better degree of mutual integration, higher impact and tensile strength, better safety factor, and can be applied in the food packaging and household goods industry. This study can provide some reference basis for the resource utilization of KGM.