Disclosed is a biodegradable polyester composition, comprising the following components in percentage by weight: i) 58-80 parts of aliphatic-aromatic copolyester; ii) 20-32 parts of starch; and iii) 0-10 parts of processing assistant agents. According to the present invention, it can be unexpectedly found during studies that the aliphatic-aromatic copolyester in which the aromatic carboxylic acid is 44 mol%-48 mol% as the total amount of diacid is used as a base resin, the crystalline peak width D of the aliphatic-aromatic copolyester is 5°C-6°C, and the starch having the particle size D(50) of 2 µm-12 µm is used as another phase; meanwhile, a processing assistant agent having the particular content is added, the polyester composition obtained by preparing has excellent transverse and longitudinal tear strength, meets industrial compost, and has more than 90% of biodegradation rate in a 12-week degradation test process.