Refractive index is an important parameter of spectacle lenses, which affects the thickness and comfort of spectacle lenses. This paper presented a method for measuring the refractive index of spectacle lenses using gemstone refractometer. The method basically met the accuracy requirements for measuring the refractive index of spectacle lenses and assembled glasses lens, and had the characteristics of fast speed, simple operation, non-destructive (or micro-destructive), low equipment investment, and direct reading of measurement results. The method had good application value.