The characterization of single mode graded index fibers by expanding modal fields in Laquerre Gaussian functions has been presented.Applying properties of Laguerre polynomials suitably and Hankel transform theory,fiber parameters,such as far field,spot size have been calculated.The final expressions are very simple and without loss of physics insight of view.Numerical examples for calculation of these fiber parameters are given and compared with exact results.Merits and the defects of by using this method have been discussed.