Isothermal crystallization of three-dimensional (3D) spherulites from the bulky melt under low shear rate flow was Studied based on new in situ observation along a direction perpendicular to the flow velocity a adient plane (XZ plane) by means Of optical microscope, where X- and Z-axes are perpendicular and parallel to the flow direction, respectively. Spherulites are rotating. A novel "spiral pattern" was found oil the surface of the rotating "half-spherulite" near the surface of the melt for the first time. The half-spherulite is named "spiralite" which enabled us to have a visible image of the rotation of Spherulite. Hence, we could detect the growth rate around the Z-axis V(Z) and that around the X-axis V(X) by using the spiral pattern. We could experimentally obtain V(Z) > V(X) in this study. From kinetic viewpoint. this fact indicates that free energy for formation of a critical nucleus around file Z-axis is smaller than that around the X-axis. From this, it is concluded that the 1 oriented melt" is formed around the 7 axis. We proved it theoretically by showing that micro shear rate (Z) on the interface around the Z-axis significantly increases and chains will be elongated even when macro is low (y < 10 s(-1)). With increase of y(Z), the chain elongation will overcome the entropic relaxation, that results in formation of the "oriented melt". Crystallization mechanism under low shear flow is proposed that file growth rate of spherulite or shish is accelerated around interface, due to formation of the "oriented melt". Finally, we proposed a possible relationship between Inch Structure and crystallization under anisotropic and isotropic external fields.