An experimental study was performed to measure the ice concentration of an ice slurry pipe flow in real time. In the present work, we suggest a refractive index measurement method and compare it to freezing point and density measurement methods. To measure the refractive index of the solution, ice particles in the ice slurry should be completely removed and a hydro-cyclone was used in this study instead of a mesh. The results from the measurement method by the refractive index coincided with those by the density within a ±5% error range when the real-time solution density was used. Even though the density measurement method showed good resolution, the results using the initial density of the solution were more than 10% in error compared to those using the real-time density. And the density measurement method has an error range 1.5 times greater than the refractive index measurement method.