In a graphene-based refractive index sensing system, the large range and high measurement sensitivity cannot be achieved simultaneously, and only the relative refractive index can be measured. In this study, a large-range absolute refractive index measurement method based on total internal reflection is proposed, which realizes the accurate regulation of a wide range of angles only through one-dimensional linear motion. The optical 4f system ensures that the position of the sampling point does not change with the incident angle. By the scanning measurement method at different incident angles, the measurement range of the refractive index can reach 1--1.5168 in theory. Through the refractive index measurement of calcium chloride solution with different mass fraction, the measurement sensitivity obtained in experiments is 7.203×10 ^-4 RIU.