Abstract: A novel least squares algorithm based on anti-WKB method and linear segment interpolation,which is called prediction-verification method, is proposed.This method takes the values calculated by anti-WKB and linear segment interpolation as approximation(prediction),then uses the least squares fitting (verification),and after that compares the linear segment interpolation based on the anti-WKB method with it. Numerical results show that the prediction-verification algorithm can effectively reconstruct the transverse refractive index profile of graded ion-exchange planar waveguide.