The propagation of light in the medium follows Fermats principle.In homogeneous medium，lightpropagates along a straight line，and in inhomogeneous medium，the propagation trajectory of light is more complex.In this paper，taking sucrose solution as the research object，the experiment of light propagation in inhomogeneous medium is designed，the related model is established，and the relationship between the refractive index of the solution and the concentration is analyzed theoretically.The gradient expression of refractive index of solution is obtained by fitting the data.