A thermoplastic starch, characterized in that the thermoplastic starch comprises (in weight parts): 20-80 parts of starch; 5-40 parts of biodegradable polyester prepolymer; the biodegradable polyester prepolymer has a molecular weight of 10,000-100,000 Daltons, a viscosity range of 0.30-1.2 dL/g, which is measured by Ubbelohde viscometer method, and a melting point range of 60-180°C; and the terminal reactive group content of the biodegradable polyester prepolymer is 1.0-20.0 meq/Kg, which is measured by a terminal group titration process; 0.01-10 parts of reaction activator; 0.01-1.0 part of catalytic deactivator; 0.01-1.0 part of antioxidant; and 5-50 parts of plasticizers; the thermoplastic starch is prepared via the below method: biodegradable polyester monomer undergoes condensation polymerization and forms, together with the reaction activator, a biodegradable polymer prepolymer having an active terminal group; and the starch reacts with the active terminal group of the biodegradable polymer prepolymer having an active terminal group to form a polyester-TPS graft copolymer, that is, the thermoplastic starch; the biodegradable polyester monomers that are involved in condensation polymerization include: hydroxyl acid, diacid or diol; the biodegradable polymer prepolymer having an active terminal group is selected from the group consisting of prepolymers containing one or more of polylactic acid, poly(butylenes succinate), poly(butylene succinate-co-butylene adipate) (PBSA) and poly(butylene adipate-co-terephthalate) (PBAT) as main chain; the reaction activator is an epoxy group reaction activator, a carbodiimide reaction activator containing unsaturated double bonds, an anhydride group reaction activator containing unsaturated double bonds, an isocyanate group reaction activator containing unsaturated double bonds or an oxazolinyl reaction activator. 20-80 parts of starch; 5-40 parts of biodegradable polyester prepolymer; the biodegradable polyester prepolymer has a molecular weight of 10,000-100,000 Daltons, a viscosity range of 0.30-1.2 dL/g, which is measured by Ubbelohde viscometer method, and a melting point range of 60-180°C; and the terminal reactive group content of the biodegradable polyester prepolymer is 1.0-20.0 meq/Kg, which is measured by a terminal group titration process; 0.01-10 parts of reaction activator; 0.01-1.0 part of catalytic deactivator; 0.01-1.0 part of antioxidant; and 5-50 parts of plasticizers; biodegradable polyester monomer undergoes condensation polymerization and forms, together with the reaction activator, a biodegradable polymer prepolymer having an active terminal group; and the starch reacts with the active terminal group of the biodegradable polymer prepolymer having an active terminal group to form a polyester-TPS graft copolymer, that is, the thermoplastic starch; the biodegradable polyester monomers that are involved in condensation polymerization include: hydroxyl acid, diacid or diol; the biodegradable polymer prepolymer having an active terminal group is selected from the group consisting of prepolymers containing one or more of polylactic acid, poly(butylenes succinate), poly(butylene succinate-co-butylene adipate) (PBSA) and poly(butylene adipate-co-terephthalate) (PBAT) as main chain; the reaction activator is an epoxy group reaction activator, a carbodiimide reaction activator containing unsaturated double bonds, an anhydride group reaction activator containing unsaturated double bonds, an isocyanate group reaction activator containing unsaturated double bonds or an oxazolinyl reaction activator.