Oyster shells are ocean waste and are available all over the world. The major composition of oyster shell is calcium carbonate which has function of anti-bacteria. If we can use them as the filler for the polymer in turn becoming polymer composites. Thus, can reduce waste and improve circular economy and this is a win-win situation. This study investigated the effect of oyster shell powder (OSP) content on the properties of PP/OSP nanocomposites. The injection molding process was done by non-foam and microcellular molding. The content of OSP is 0, 5, 10, and 15 wt% respectively. Tensile strength showed that the elongation increased as the OSP content increased. The PP/OSP composite has the maximum tensile strength at the OSP loading of 5 wt%. TGA results showed that it has the highest thermal degradation temperature at 434.4℃ ＠7 wt% OSP. Rheological test showed that viscosity decreased as the OSP content increased. Effect of OSP loading on the morphology of the foamed composites are discussed.