A non-destructive method for measuring the refractive index of spectacle lenses is proposed.The refractive index of spectacle lenses is measured by measuring the lens' reflectance in visible light region and fitting the curve by Gauss-Newton iteration method.And the Cauchy model is used to analyze the dispersion phenomenon.The experimental results show that the relative error is less than 2%,and the measurement accuracy can basically meet the judgement of the lens refractive index.