The invention provides a preparation method of an anagliptin intermediate. The preparation method comprises the following steps: (1) N,N-dimethylformamide (I) and acyl chloride are subjected to a Vilsmiere reaction to produce a Vilsmiere reagent, bromoacetic acid (II) is dropwise added to the Vilsmiere reagent for a heating reaction, hydrolysis is performed, and dicarbaldehyde acetaldehyde (III) is obtained; (2) dimethyl acetaldehyde (III) and 3-amino-5-methyl pyrazole (IV) are dissolved in an alcohol/sodium alcoholate system, heating and reflux stirring are performed, and 6-carbaldehyde-2-methyl-pyrazo[1,5-a]pyrimidine (V) is produced; (3) 6-carbaldehyde-2-methyl-pyrazo[1,5-a]pyrimidine (V) is oxidized in strong base to produce 2-methyl-pyrazo[1,5-a]pyrimidine-6-carboxylic acid (VI). Thereaction steps are simplified, operation is convenient, few three wastes are produced, and the yield is high.