Abstract: It is well known that the absorbance-concentration relationship of a chemicalcomponent may deviate from Beer's law with certain chemical cause, and errors of aborhancemeasurement propagate and multiply in mathematical operation. But there are difficulties in carryingout experiments on large systems of chemical components to ascertain the real relationship , andstatistical simulation spectrophotometry-SSS for short ,or Monte Carlo simulation spectropho-tometry——has been developed for the assay of medicaments in compound formulations.The keystep of SSS is to build a model based on a collection of limited but sufficient actual data , then themodel will provide the numerical imitation——giving simulation data——of the real sum-upabsorbance-concentration relationship of individual medicaments at several sensitive wavelengths.The method of stepwise regression has been used in the present study on Naoqingpian tablets,acompound formulation of two medicaments.For the reliability of this SSS ,an analysis of variance hasbeen performed on the assay data of cross- classification to separate and estimate the variationsassociated with instrument and operator. SSS is accurate , rapid and practicable ,and promises well tobe adopted as an official assay method of some compound formulations.