Self-organization of microstructures in interfacial growth has been intensively studied in the past decades. Ordered structures can be spontaneously generated in the interfacial growth by stress-induced instability. Yet up to now most researches concentrate on two-dimensional systems such as thin films. In crystallization, spontaneous alignment of crystallites and hence ordered crystallite aggregate can be observed, yet the mechanism remains unclear. One example is the spherulite growth, in which crystallites are continuously twisted or titled. Another example is the aggregation of NH4Cl crystallites in agarose gel, where the orientation of each crystallite becomes closely correlated. Ultimately branches with regular zigzagged microscopic features are formed. By changing the driving force of crystallization, aggregate with spatial periodic roughening transition on the surface can be observed, which arises from the regular change of crystallographic orientation of the crystallites (part of these results have been published in Phys. Rev. Lett., 80, 3089 (1998); J. Crystal Growth,208, 687 (2000)). Here we report an in-depth study of the origin of the long-range correlation of the crystallographic orientations in the aggregate investigated by means of micro-X-ray-diffraction, atomic force microscopy and in-situ optical observation. It is shown that the topographic regularity of the aggregate originates from the consecutive rotation of the crystallographic orientation in the nucleation-mediated growth. This effect may occur when nucleation takes place in a region with inhomogeneous surface tension. It may help to clarify the long-range orders observed in our experiment and possibly the spherulite growth in general.