The Liaohe Group is a major component part of the Palaeoproterozoic Jiao-Liao-Ji (Eastern Shandong-Liaoning-Jilin) arc-continent collisional orogen. Recent PTt path studies'have revealed multiplicity of PTt paths in this orogen without a fixed or unified model of PTt paths. The origin of the opposite directions of the PTt paths of the north part and the south part of the orogen was due to the differences of their architecture,. deformation processes and spatial distributions of synmetamorphic and syndeformational granites, that is to say, the complexity of PTt paths in different space locations depends on the continental dynamic process and environment. Metamorphism of the South Liaohe Group and Gaixian Formation-complex occurred in four stages. Isobaric or small-amplitude pressure increase, rapid rise of temperature in the early and middle metamorphic stages resulted from granitic magma underplating in the middle-lower crust and its induced bedding-parallel detachment and thinning of sedimentary covers. In the peak metamorphic stage, isothermal pressure increase (the Gaixian Formation-complex) and temperature and pressure increase (the South Liaohe Group) were related to constrictive compression and thickening. In the last stage, different denudation caused decompressive cooling (the Gaixian Formation-complex) and nearly isobaric cooling (the South Liaohe Group). In the North Liaohe Group, in the early and the middle metamorphic stages, because less granite was emplaced and thickening was generated by northward sliding and overlapping of the South Liaohe Group and Gaixian Formation-complex and moreover the metamorphism only depended on normal thermal conduction and radiogenetic heating. Pressure and temperature reached peak values simultaneously in the setting of shortening at the early peak metamorphic stage, and then isothermal rapid pressure decreased was related to tectonic denudation. In the metamorphic stage, the North Liaohe Group experienced a process of decompressive cooling, as is the case with the Gaixian Formation-complex. Comparison of the continental dynamic processes of the North and the South Liaohe Groups in the early and the middle metamorphic stages suggests that they were exactly antithetic processes which determine the opposite directions of their PTt paths. Therefore, the PTt paths mainly depended on the initial thermal structure and continental dynamic processes of the orogen. At last, an "underplating + delami-nation" model is proposed to interpret the metamorphic dynamic processes of the Liaohe Group.