Rh6G random laser systems are obtained by choosing four solvents (methanol, ethanol, glycol, dimethylsulfoxide) with different refractive indices to disperse Rh6G mixed with 100 nm AlN spherical nanoparticles. It is experimentally investigated that the spectral and threshold characteristics of the Rh6G random laser behaviors. As for the spectra, typical emission evolution spectra are observed. The peak positions vary with the change of solvents, and the reason for the variation is the absorption of the samples. For the threshold feature, the experimental results indicate that the threshold of the random laser depends on the refractive index of the surrounding solvents. The larger the refractive index of scatterers or smaller the refractive index of solvent is, the smaller the threshold will be. The theoretical explanation based on Mie scattering theory for this phenomenon is made. The low threshold random laser is attributed to low refractive index of solvent, which influences the scattering strength, leading to a smaller transport mean free path.