With its completely biodegradable ability, good physical and processing properties, and biocompatability, PHA has become the most attractive alternative to take the place of chemo-plastics and eliminate environmental pollution caused by chemo-plastics. Small-scale commercial production has been realized by bacterial fermentation, but thus produced PHA is too expensive to compete with chemo-plastics. However, it is very prospective to lower biodegradable plastic price by producing PHA in transgenic plants. Presently PHB/PHBV biosynthetic genes have been transferred into plants and expressed, but it is still far away from meeting the demands of commercial production. Enhancing research on the regulation of carbon and fatty acid metabolisms, and their biochemical and molecular mechanisms is the key to achieving this aim.