This paper presents a liquid fiber displacement measurement method for m easuring the refractive index.Firstly,the laser interferometry is used to design optical measuring system of refractive index of liquid,and based on the elimination of laser speckle theory,a pinhole filter designed to eliminat e speckle reasonable is and further improve the system′s anti-jamming capabil ity.Secondly,after analyzing the displacement measurement methods the measurement system in, we propose a fiber optic displacement measuring method,and apply fiber optic displacement sensor for eliminating the traditional fringe counting to achieve high-precision measurement of displacement.The measurement resolution can reach up to micron level.Thirdly stepper motor drive system is used to drive the optical system elements to implement an automatic change of optical pat h difference,and the driving resolution may nanometer grade.Finally,the overall measurement system is built for measuring the refractive index of liquid with w ater and solution as experimental subjects.The capacit y of the measured sample is less than 0.001mL.The experimental results show tha t refractive index measurement precision of pure water can reach 0.0015,and refractive rate measurement precision of NaCl solution can reach 0.0021,which shows that the measurement method can realize non contact,high precision,intelligent measurement of liquid refractive index.