The invention relates to rare earth complex modified cold-resistant fluororubber gross rubber and a preparation method thereof. The gross rubber is prepared by blending fluororubber crude rubber, a rare earth complex, an acid-acceptor, a reinforcing filling agent, a vulcanizing agent and an accelerating agent. The preparation method of the gross rubber comprises the following steps of: (1) performing plastication covered rolling on the fluororubber crude rubber, and adjusting the roller spacing to ensure that spacer gel exists between two rollers; (2) adding the rare earth complex, the acid-acceptor, the reinforcing filling agent, the vulcanizing agent and the accelerating agent in sequence, controlling the roller temperature to be between 40 and 50 DEG C, taking down thin sheets when the rubber materials are uniformly mixed, and placing the gross rubber for 24 hours; and (3) controlling the roller temperature to be 40 DEG C, adjusting the roller spacing to be 0.2mm, performing re-milling to beat triangular covered thin sheets for more than 10 times, adjusting the roller spacing to be 2mm, and discharging the sheets to obtain the gross rubber. The rare earth complex modified cold-resistant fluororubber gross rubber has the advantages of good cold resistance and medium resistance, and the preparation method is simple and convenient, low in cost, and easy to realize industrial production.