Abstract: This paper provides a basic principle and experimental technique of signal multiplier spectrophotometry. Quantitative analysis of three component mixture can be done without sample separation. This method was investigated to assay the contents of aspirin, acetaminophen and caffeine in compound tablets of acetaminophen by using a manual spectrophotometer (UV 7520). The selection of optimal wavelength pairs is performed through the program with a microcomputer. The contents of the three components could be analyzed when the absorption values at 4 wavelengths were determined. The average recoveries for each component are 99.6±0.36%, 100.0±0.37%, and 100.6±0.74, respectively (95% confidence level). Linearity and precision of analysis are good and the method is easy to employ.