Polyethylene glycol - polycaprolactone block copolymer (PEG - b - PCL) ultrathin films were fabricated via the solution spin - coating and orientation method. The crystal morphology, structure, and the dependence of orientation on the thickness of PEG - b - PCL ultrathin films were systematically characterized using atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The results indicate that orientation is advantageous for the crystallization of copolymers.As the orientation speed increases, the dewetting pore size expands, and the thickness of the lamellae grows. Additionally, the lamellae transform from porous lamellae into dendritic crystals.Therefore, the crystal structure of ultrathin films can be regulated by orientation.