The invention discloses a full-degradable thermoplastic composite material which is prepared from polylactic acid and starch which serve as base materials, PBAT and PCC, a sheet which is prepared from the material and is applicable to hot pressing and forming, and a preparation method thereof. The main components of the full-degradable thermoplastic composite material and the sheet of the invention are polylactic acid, starch and the like with biological sources, and the material and the sheet thereof can be degraded into water and carbon dioxide under the condition of compost, thereby saving a large amount of energy and reducing the environment pollution. The full-degradable thermoplastic composite material and the sheet thereof of the invention are mainly used for manufacturing sheets which are processed through plastic suction in the packaging industry, can be applied in the processing of disposable cups, disks, bowls, plates, boxes and the like through a plastics suction method, are widely applied to the packaging of food, vegetables, fruits, drinks, dairy food and industrial parts, and have stronger popularization significance.