In this study, we propose a theoretical analysis for the Ti-diffused Nd:MgO:LiNbO3 waveguide lasers with nonuniform concentration distributions by using the evolution equations of the pumping light and amplified spontaneous emission (ASE), The concept that ASE is the origin of the laser light is applied, and, the evolutions of the pumping and ASE are calculated by considering the feedback from the reflectors al the waveguide ends, Furthermore, because this analysis also considers the spatial distributions of the Nd and Ti concentrations, pumping, and ASE: light in the waveguide laser, it is appropriate for a case involving arbitrary Nd and Ti concentrations and waveguide profile, Also, the laser characteristics of the Ti-diffused channel waveguide structures in the Nd-diffused MgO:LiNbO3 and Nd:MgO:LiNbO3 crystals are analyzed and compared, Moreover, theoretical data correlate well with the experimental results reported previously.