The invention relates to a preparation method of a negative plate of a chemical battery, which comprises the steps of sizing, drying and rolling, wherein the sizing step is continuous, double-side sizing and single-side sizing are operated alternatively, and the single-side sizing is adopted on a surface which has no corresponding positive surface; and that the double-side sizing and the single-side sizing are operated alternatively refers to that the double-side sizing is adopted on a section of the negative plate, the single-side sizing is adopted on a next section, then the double-side sizing is adopted again, and the cycle is repeated.