Abstract Zinc oxide nanocrystals were prepared by homogeneous precipitation method using urea and zinc nitrate as raw materials. The orientation adhesion of nanocrystallites formed by connection of crystallites was discussed by the growth unit model of anionic coordination polyhedrons. It was shown that zinc oxide nanocrystal growth was more easily to occur along c-axis, which was primarily formed by the connection of positive hexagonal cone faces p ( 1 0 1 ¯ 1 ) and negative hexagonal cone faces p ′ ( 1 0 1 ¯ 1 ¯ ) , secondly by the positive polar faces c(0 0 0 1) and negative polar faces − c ( 0 0 0 1 ¯ ) .