An irradiance distribution model for laser triangulation displacement sensors is proposed, which is more suitable for practical applications than the geometric optical model (GOM). Based on the irradiance distribution model, a convergence algorithm is developed. Compared with the design parameter optimized method based on the GOM, the convergence algorithm can be used for optimization of not only the traditional design parameters including view angle and object distance but also the waist of the source laser beam. Additionally, using this convergence algorithm, the nonlinearity can be evaluated in the design stage. To validate the convergence algorithm, two example cases are performed. The results show that the nonlinearities are reduced to 6.3098 and 5.7946  μm, respectively.