Regenerated cellulose is a class of material formed by dissolving and regenerating cellulose into certain product. Regenerated cellulose has potential to be developed into environmentally friendly biodegradable plastic especially because abundance of cellulose in nature. Cotton is one of main source of cellulose that consist 86 – 98% of its mass. In this research, waste cotton from textile industry are used as source of cellulose which extracted via sulfuric acid hydrolysis process with concentration varied in 0,5; 1; 1,5; and 2 M in 100°C for 2 hours to obtain cellulose with various molecular weight. Regenerated cellulose is prepared by dissolving cellulose with NaOH 7 wt%/Urea 12 wt% which then formed by solution casting method. Molecular weight of cellulose was investigated by viscosity average molecular weight method using Ubbelohde viscometer. Thermogravimetry Analysis (TGA), water absorption test, and biodegradability test are conducted to investigate the influence of molecular weight to the thermal degradation, water absorption, and biodegradability of obtained regenerated cellulose plastic respectively. The result showed that the decrease of molecular weight causing the thermal degradation and water absorption to decrease but increasing the biodegradability of the obtained regenerated cellulose plastic. Highest thermal degradation temperature hailed resulted from usage of cellulose with molecular weight 2.73 x 104 g/mol which is 316°C as the lowest water absorption and highest mass loss after soil burial test is resulted from molecular weight 1.94 x 104 g/mol with value 49,60% and 50,55% respectively. This research showed that regenerated cellulose is promising to be applied as biodegradable plastic.