Based on the characteristics of non - contact high measurement accuracy and ease of use, laser triangulation distance measurement has been widely used in scientific research and industrial production practice. Displacement measurement is determined from the shift of laser spot on an imaging system′s photo sensitive surface . Different application normally requires selection of different polynomial fitting coefficient terms between the two. Proper selection of polynomial terms is very important for realizing high speed and high accuracy in measurement. In this paper, regarding the non-linear relationship between the measured surface displacement y of laser triangulation displacement measurement and the displacement x of the imaging spot on the photosensitive surface, systematically analyzed the error sources due to polynomial fitting of y as a function of x. A miniature laser triangulation displacement sensor were built, Based on the experimental measurement data, it is verified that the laser triangle displacement measurement device satisfies the Scheimflug condition. According to the experimental measurement values and the displacement values calculated by polynomial fitting, a quality factor Q is defined to judge the quality of the fitting, and the optimal number of polynomial terms is determined by calculating the Q factor.