Abstract: The present invention relates to method for the preparation of 3-fluoroalkyl-1-methylpyrazol-4-carboxylic acid, wherein it comprises the following steps: step 1, fluoroacetyl fluoride derivative shown in Formula I undergoes condensation with dimethylamino vinyl methyl ketone, as a result, 3-dimethylamino methylene-fluoro-2,4-pentanedione derivative shown in Formula II is formed; step 2, ring closing reaction takes place between said 3-dimethylamino methylene-fluoro-2,4-pentanedione shown in Formula II and methylhydrazine, in this way, 3-fluoroalkyl-1-methyl-4-acetyl pyrazol derivative shown in Formula III is obtained; step 3, the said 3-fluoroalkyl-1-methyl-4-acetyl pyrazol derivative shown in Formula III is oxidized in the presence of alkali, and then acidified, in this way, 3-fluoroalkyl-1-methylpyrazol-4-carboxylic acid shown in Formula IV is formed.