Polyhydroxyalkanoate (PHA), as a biosynthesised intracellular polyester, has attracted much attention due to its excellent biocompatibility, biodegradability, and physical and chemical properties similar to those of synthetic plastics. However, there are still limitations in the comprehensive performance of PHA as a single polymer. The structural diversity of PHA offers the possibility of its modification by physical, chemical, and biological modification methods to enhance its properties for a wider range of applications. PHA-modified materials showed promising applications in the fields of medicine, agriculture and packaging. The modification methods of bio-based biodegradable material PHA and its application studies are reviewed, aiming at providing new ideas and theoretical guidance for the industrial application of PHA.