According to the physical model of laser-assisted pre-stress forming, a set of dimensionless quantities was proposed and a similarity criterion was established with equation analysis and dimensional analysis, for the physical quantities such as temperature field, forming efficiency, and elastic energy conversion. Two models with a model ratio of 1∶3 under geometry and physical similarities were analyzed with finite element methods. The results show that with the models satisfying similarity criterion, the output quantities are of physical similarity in correspondence with the input quantities.