Additive manufacturing via selective laser sintering (SLS) makes it possible to create parts by fusing successive layers of powdered material, forming surfaces with significant dimensional inaccuracies and shape deviations. To improve the accuracy of products made using SLS, the objectives were to identify the primary components of the shape formation error that arises during the layered building and to describe the influence of the main factors on them analytically. A structural mathematical model has been developed to describe the formation of part dimensions obtained by layered building. Compensation for the relative dimensional error of products caused by shrinkage is done by applying a technological transformation (non-proportional scaling along the X, Y, and Z axes, considering the specified functions) of the triangulated 3D model at the stage preceding materialization. As a result of the analysis of the structural model of part dimension formation, a parametric model has been developed that considers the product's dimensional states, the transition between which is influenced by the primary shape formation errors and parameters of technological preparation of triangulated models. The sufficiently high adequacy of the obtained model for the Vanguard HS Si2 system has been experimentally confirmed. As a result, it was possible to improve shape formation accuracy by applying preliminary technological transformation.