Department of Mathematics, Indiana University, Bloomington, IN 47405(Dated: February 4, 2008)The main objective of this article are two-fold. First, we introduce some general principles on phasetransition dynamics, including a new dynamic transition classi cation scheme, and a Ginzburg-Landau theory for modeling equilibrium phase transitions. Second, apply the general principlesand the recently developed dynamic transition theory to study dynamic phase transitions of PVTsystems. In particular, we establish a new time-dependent Ginzburg-Landau model, whose dynamictransition analysis is carried out. It is worth pointing out that the new dynamic transition theory,along with the dynamic classi cation scheme and new time-dependent Ginzburg Landau models forequilibrium phase transitions can be used in other phase transition problems, including e.g. theferromagnetism and superuidity, which will be reported elsewhere. In addition, the analysis forthe PVT system in this article leads to a few physical predications, which are otherwise unclearfrom the physical point of view.