Abstract: cloroprenaline hydrochloride (a), bromhexine hydrochloride (b) and decloxizine hydrochloride (c) are three main components in clorprenaline compound tablet. The serious overlapping bands of their absorption spectra cause the interference in the determinations, especially the component of (a) which has both minor content and low absorption coefficient, thus making the analysis difficult. In this paper, the interference from matrix is eliminated by using first order derivative transformation. In combination with complementary tristimulus method and with the technique of additions, the concentrations of three components in tablets can be suecessfully determined simultaneously. A software developed in this laboratory makes possible the ease of parameter selection, reporting data in various formats and printing figures of dissolution process, showing a clear locus. This method will be of value to quality control in manufacturing process and to the research of the dissolution dynamics of tablets in simulated stomach.