Abstract: Referring to the detection method of antipyrine content in Antongding injection in the first book of Chinese Veterinary Pharmacopoeia（2005）,a set of solutions were prepared.Supposing the same content of antipyrine reference substance and the same pH,the concentration of p-dimethylaminobenzaldehyde reagent was gradually increased and the absorbency was measured after constant volume approach and other treatments.After too much higher or lower absorbency was eliminated,the sample with the absorbency of 0.573 6 was selected.And the added chromogenic reagent was 6 mL p-dimethylaminobenzaldehyde solution.In order to validate the reliability and operability of the concentration of the chromogenic reagent,the chromogenic reagent at this concentration was added to different solutions and samples in a series of standard curves and the results showed that the recovery rate of samples was 99%～105%.