The binding reaction of cytidine 5′-phosphate(5′-CMP) with Alizarin Red S(ARS) was studied in the buffer solution(pH=4.56) as functions of temperature, time, ionic strength and interference of inorganic substance, biological substance and surfactant by UV-Vis spectrophotometry. It was found that the bathochromic shift of the maximum absorption peak of the complex was 90 nm. The apparemt molar absorptivity wasε=3.80 ×10^3L/(mol·cm), the binding number was n=13, and the linear range of reaction was 0～14mg/L.
