OBJECTIVE：To set up a method to determine the content of hyoscymine alkaloides in belladonne tablet by spectrophotometry.METHOD:Hyoscymine alkaloides reacts with bromomethyl phenol to produce a colorful ionic couple at a certain pH solution.Product is extracted using CHCl3 solvent and determined by spectrophotmetry.The detection wavelength is 415nm.Atropine sulfuric acid is used as reference standard.RESULTS:The calibration curve is linear within the range of 0～17.5μg/ml for hyoscymine alkaloides.The average recovery is 101.1% and the related standard deviation is 1.0%.CONCLUSION:The method is simple,accurate and practical for the determination of hyoscymine alkaloides in belladonne tablet.