The invention relates to a preparation method of a pyrazole derivative. An intermediate compound shown in formula IV and a fluoro-acetic halide derivative shown in formula V react to produce a fluorine-containing intermediate compound shown in formula VI, the fluorine-containing intermediate compound shown in formula VI is hydrolyzed under the action of acid and subjected to pyrazole ring closingto produce 3-fluoroalkyl-1-methyl pyrazole derivative shown in formula VII, and the 3-fluoroalkyl-1-methyl pyrazole derivative shown in formula VII reacts and then is acidized under the alkaline condition to produce 3-fluoroalkyl-1-methyl-1H-pyrazole-4-carboxylic acid shown in formula VIII. The invention also relates to a structure of the intermediate compound of the pyrazole derivative obtained with the preparation method. The preparation method of the pyrazole derivative is suitable for industrial production.