Abstract: Through the introduction of double-circulating measurement, the accurate measurement of complex refractive index of liquid was achieving by using the Brewster Angle measurement technology. The p polarized light went into interface of the bottom of an isosceles prism and sample to be measured . After rotating the prism step by step, the experimental curve of the relationship between the total light intensity reflectivity of the sample with the incident angle was made. Based on the Fresnel formula and Confucianism's specific law, the basic principle of the complex refractive index of liquid is analyzed, the refractive index and extinction coefficient of sample can be obtained by using binary fitting. Appling corresponding experiment system, the complex refractive index of the Indian ink, Fat Emulsion Injection and Diiodomethane refractive index matching liquid was measured and the samples experimental curve of the refractive index, absorption coefficient versus the concentration of liquid was composed. Experiment results showed that the measuring precision of liquid refractive index and the absorption coefficient were about 0.000 2 and 0.000 1 with high accuracy and stability. Meanwhile, the range of liquid refractive index is not limited by prismatic refractive index.