Abstract: In order to improve the efficiency of detection for hydrocyanic acid content in flaxseed,while ensuring its accuracy,The pretreatment method of isonicotinic-barbituric acid colorimetric method had been optimized by response surface methodology.A quadratic polynomial regression model was fitted using a three-factor,three-level Box-Behnken design and analyzed using response surface methodology to obtain the optimal extraction conditions.The result showed that the best extraction technology conditions was at the ratio of solvent and material50∶ 1,with 10 g / L concentration of sodium hydroxide absorbing liquid and extracting for 45 min.The hydrocyanic acid extraction ratio could reach 96.12%.This method is true and reliable,can be used to detect large quantities of hydrocyanic acid in flaxseed.