Abstract: Highly filled polyethylenestarchcalcium carbonate ternary composite was prepared and compost degraded according to ASTM D6400 standard. The degradation behavior of the composite was studied by melt flow indexes (MFI), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and so on. Results showed that the MFI reached a minimum value around the first month of compost, the crystallinity of the composite decreased, the morphology of the composite changed significantly and the starch content decreased continuously with the extension of compost time. After composted for 3 months, the elongation at break, impact strength and flexural strength were decreased by 28.0%, 24.5% and 25.5%, respectively. But the tensile strength changed little with the extension of compost time.