Quartz fiber with diameter of 93 μm is immersed into a low refractive index solution, which is mixed with ethanol and ethylene glycol doped by rhodamine 6G dye molecules. Pumped by evanescent-wave along the fiber axis, the lasing wavelength of whispering gallery mode (WGM) is found blue-shifting with the refractive index of dye solution increasing. The experimental observations are well explained by the γ(λ) curve, which is deduced from the four-energy level model of dye lasing from a WGM fiber laser and caculated by the ratio of molecular density for the upper and total lasing energy levels.