An analysis of TM modeand effective refractive index in c-cut Ti-diffused Nd:LiNbO3 strip waveguide lasers hasbeen carried out at the laser wavelength 1085 nm and pump wavelength 815 nm by usingvariational technique. The mode size and effective refractive index as function of thecontrollable waveguide fabrication parameters(initial Ti-strip width W, diffusiontemperature T and initial Ti-strip thickness H) have been calculated for severallower-order modes. The single-mode and cut-off conditions were discussed. The numericalresults are compared with previously published experimental data.