The biodegradable plastics have been synthesized from janeng starch with the addition of ZnO and Glycerol as plasticizers. The process has used ZnO with variation of concentration by 1%, 3% 6%, then Glycerol with volume 1 ml, 3 ml, and 6 ml. The utilization of 6% ZnO and 3 ml of glycerol showed the highest tensile strength of 2.8 kgf/cm 2 ; conversely, the highest percent elongation was obtained at 1% ZnO with addition 6 ml glycerol to be 4.5%. The lowest water absorption was captured in the composition of 6% ZnO with the addition of 1 ml of glycerol, which was equal to 2.9%, and the decomposition process occurred for 27 to 36 days.