Improved scaling rules for nonlinear film waveguides given by Marie Fontaine are improved.Using three independent dimensionless parameters,formulas for characteristic analysis,dispersion curves and curves for optical power dispersion versus modal indices are presented for nonlinear Kerr-type film waveguide with linear substrate and cladding (LNL planar guides).The present method can be easily extended to other type nonlinear planar guides NLL,NNL,and NNN,etc.