Biodegradable plastics are one of the breakthroughs in the effort to reduce plastic waste. A biodegradable plastic can be produced from microalgae with high protein content, such as Spirulina platensis. Microalgae were mixed with a polymer; polyvinyl alcohol was used in this research to create the bioplastics. Other materials were glycerol as a plasticizer to increase flexibility, and maleic anhydride as a compatibilizer to strengthen the bond between the microalgae and polymer. This research aims to produce biodegradable plastic with mechanical properties similar to conventional plastics, i.e. tensile strength of 26.37 kgf/cm
and elongation of 55%. This research varied the amount of maleic anhydride, which were 0% wt, 2% wt, 4% wt, and 6% wt. Mechanical properties, i.e. tensile strength and elongation and surface morphology with SEM have been analyzed. Based on the experiment, the excellent compatibilizer composition for bioplastic film is 6% wt, which shows the tensile strength at 28.26 kgf/cm
and elongation at 59.17%. Surface morphology comparison with SEM shows that bioplastic film with compatibilizer has more uniform surface than without compatibilizer.