The presence of grain boundary (GB) premelting can alter macroscopic properties of polycrystalline materials, which lead to catastrophic material failure as exemplified by hot cracking during high temperature processing of metallic alloys. Since the premelting is considered to occur in a very limited region, it is difficult to image and to measure thermodynamic properties of nanoscale width of liquid films. At the microscopic level capturing crystalline details, atomistic modeling techniques such as Monte－Carlo (MC) or molecular dynamics (MD) have been widely adopted, however, these methods can't be used to observe morphology of GB at atomic level. Phase field crystal (PFC) has the advantage of resolving the atomic scale density wave structure of a polycrystalline material, it naturally incorporates elastic and plastic deformations and multiple crystal orientations and can be used to study a host of important material processing phenomena. The GB premelting and melting were investigated by PFC method, microstructure evolution of premelting and melting under different misorientation angles were discussed and the film width of GB was quantitively compute in terms of the excess mass method. The results showed that the liquid film appears as the melting point is approached from below, and the morphologies of liquid film are related to misorientation angle. When misorientation angles are high－angle GB, the liquid film are homogeneous. For low－angle GB, the individual dislocations which are surrounded by liquids are uniform distributed in the GB, as the melting point is approached, structure transition occurs as follows: the dislocations form pairs and the original liquids are also combined a big “liquid pool”. This structure transition not only appears during the period of premelting, but also occurs in the overheated stage, which presents a jump in the film width picture. Critical wetting angle is 12° computed by PFC method, it is more closer to the actual results than the value obtained from the Read－Shockley theory.