A novel method for measuring refractive index of liquids based on a liquid drop formed at the end of fiber sensing probe is reported. The effect of the drop is like a plane-convex lens whose refractive index equals to that of the tested liquid. The light from transmitting fiber successively experiences refraction of the liquid drop to air interface,the air to liquid drop plane interface and the air to liquid drop,and is finally collected by the receiving fiber. According to Fresnel′s formula,the transmission coefficient and reflection coefficient at these interfaces dependes on the refractive index of the tested liquid. Based on spherical refraction imaging and reflective intensity modulation,the light transmission path is analyzed,and the mathematical mode between the intensity of the collected light and refractive index is set up. NaCl solutions with different concentrations are tested. The experimental results indicate that the method can be used for measuring the refractive index of the liquid.