Abstract： Objective To employ a laser triangulation method for measuring post-gel and postvitrifi-cation polymerization shrinkage of composite resins.Methods A novel experimental set-up capable of measuring real-time shrinkage strain was utilized.Total shrinkage of the five composite resins was measured.The measurements of post-gel and post-vitrification linear shrinkage as a function of the gel-point and vitrification transition point were also carried out in the study.Results Gel point of the five composite resins ranged from 0.77 s to 1.59 s,while vitrification transition point ranged from 1.99 s to 6.33 s.Postgel shrinkage ranged from 33.35 μm to 53.18 μm and post-vitrification shrinkage ranged from 16.43 μm to 30.58 μm.Total shrinkage ranged from 39.25 μm to 64.84 μm.Significant differences in the gel point and vitrification transition point among the five composite resins were found( P ＜ 0.01 ).Significant differences in the post-gel shrinkage,post-vitrification shrinkage and total shrinkage among the five composite resins were found( P ＜0.01 ).The ranking of post-gel and post-vitrification shrinkage of these composite was different from that of their total shrinkage.Conclusions Laser triangulation method is suitable for measuring clinically significant post-gel and post-vitrification shrinkage.