In order to improve the dimensional accuracy of parts, the flat dimensional precision and height dimensional precision were sintered by the selective laser sintering rapid prototyping experiments. Through experiments, the average dimensional discrepancies of XY and Z were obtained. The shrinkage rates of the SLS part for polystyrene powders and the correction factor on horizontal were got through calculation. The result shows that the correction factor on horizontal is 1.003 and the vertical dimensional discrepancy is 1.16 mm, and is not affected by the dimension size of Z. The experiment result shows that the dimensional accuracy of sintering part for correction digital model has greatly improved. The average dimensional discrepancy of XY is less than 0.06 mm, which satisfies the requirement of production.