The invention discloses diatomite and kaolin thermal-insulation film master batch and a preparation method thereof. The diatomite and kaolin thermal-insulation film master batch comprises the following components in percentage by mass: 22%-26% of diatomite, 30%-34% of kaolin, 32%-35% of polyethylene, 2%-3% of an aluminate coupling agent, 0.5%-0.8% of stearic acid, 0.3%-0.5% of calaium strarate, 2%-3% of paraffin, 1%-2% of PE (polyethylene) wax and 0.5%-0.8% of an antioxidant. The raw materials are mixed in a high-speed mixer in stages and then are extruded by a same-direction parallel twin-screw extruder to prepare the master batch. According to the diatomite and kaolin thermal-insulation film master batch and the preparation method thereof disclosed by the invention, the diatomite, the kaolin and the polyethylene are mixed and modified, the adding proportion of the diatomite to the kaolin is controlled to be 52%-60% to prepare master batch, the infrared-ray transmission rate of mulching film prepared by 5%-15% of the match batch can be reduced by 31%-34%, and the thermal insulation effects are obvious.