Biodegradable plastic are renewable packaging technology that are bio-based made of starch. The use of starch as a manufacture of bioplastic has great potential due to in Indonesia has various biodiversity of starch-producing plants. The objective of this research was to determine effect of cassava starch addition to hardness, density, moisture absorption, and biodegradability of bioplastic. The methods is a synthesis of bioplastic using a casting procedure ie mixing cassava starch at various concentrations 2%, 3%, 4%, and 5% (b/v) into the glycerol. This was demonstrated of bioplastic hardness and density of 31.56; 46.78; 52.34; 67.99 Shore A and 1.164; 1.178; 1.184; 1.191 g/cm3. Revealed that complete decomposition could be achieved on the 12, 13, 14, and 15 days. It shows that the cassava starch addition can improve hardness, density, moisture, and accelerate the decomposition process.