Abstract: The quasi-bound state in the continuum (quasi-BIC) is a special resonant mode in a metasurface with a very high quality factor that can greatly enhance the light-matter interaction and has important applications in fluorescence enhancement, nanolaser, optical sensing, and nonlinear optics. In this paper, we study the application of quasi-BIC dielectric metasurface for refractive index sensing based on the theory generated by our previous quasi-BIC. The basic structure of the sensing device is given, the preparation of the sample optofluidic structure is completed by using electron beam lithography combined with injection molding process, and the performance is initially tested. The results showed that the metasurface has two high-Q quasi-BIC resonance peaks (1.523 µm and 1.570 µm, with quality factors of 3069 and 4071, respectively), thanks to the new strategy of quasi-BIC generation. The test experiments with four refractive index solutions (n=1.450/1.462/1.470/1.480, respectively) as samples showed that both resonance peaks could complete the refractive index detection with the sensitivity of 452 nm/RIU and 428 nm/RIU, respectively, and the performance evaluation indexes FOM were 376.7 and 372, respectively, which are better than the existing literature. The linearity between resonance wavelength and refractive index is good, showing the potential of quasi-BIC metasurface in refractive index sensing.