NOVELTY - Preparing 1,3-trifluoromethyl-1-methyl-pyrazole-4-carboxylic acid, comprises condensing by mixing e.g. cyanoacetic acid and N,N-dimethylformamide dimethylacetal, reacting and drying, acylating by reacting e.g. the first intermediate solution and trifluoroacetyl chloride, cyclizing by mixing the second intermediate solution and 40 wt.% methyl hydrazine aqueous solution, washing using diluted acid aqueous solution to obtain the third intermediate solution, hydrolyzing by mixing e.g. the third intermediate solution and inorganic alkali, reacting, filtering, and drying to obtain the product.    USE - The method is useful for preparing 1,3-trifluoromethyl-1-methyl-pyrazole-4-carboxylic acid (claimed).    ADVANTAGE - The method: has simple synthesis process, short production cycle and low production costs; ensures high total yield, causes less pollution; is suitable for industrial production; and produces product, which is an intermediate to penthiopyrad fungicide.    DETAILED DESCRIPTION - Preparing 1,3-trifluoromethyl-1 -methyl-pyrazole -4 -carboxylic acid, comprises: (a) condensing by mixing cyanoacetic acid, N,N-dimethylformamide dimethylacetal and an organic solvent, preserving temperature and reacting, cooling, washing using saturated sodium bicarbonate aqueous solution, drying using anhydrous sodium sulfate for 2-3 hours, filtering to remove sodium sulfate to obtain the first intermediate solution; (b) acylating by mixing the first intermediate solution, organic alkali and trifluoroacetyl chloride, preserving temperature and reacting, washing using water and separating to obtain the second intermediate solution; (c) cyclizing by mixing the second middle solution and 40 wt.% methyl hydrazine aqueous solution, preserving temperature and reacting, washing using diluted acid aqueous solution to obtain the third intermediate solution; and (d) hydrolyzing by mixing the third intermediate solution, inorganic alkali and water, preserving temperature and reacting, cooling, separating the aqueous layer, adjusting the pH to acidic using an dilute acid, separating the solid, filtering, and drying to obtain the product.