As an important semiconductor metal oxide, various methods have been developed for preparation of ZnO architectures owing to their excellent properties and extensive applications. In this paper, two kinds of 3D flower-like ZnO architectures assembled with numerous nanosheets were successfully synthesized by a simple hydrothermal route assisted by sodium dodecyl sulfate (SDS), origining from the different alkali environment created by urea and hexamine (HMT). SEM and TEM results revealed that the two products had hydrangea-like and rose-like nanostructures with uniform particle sizes, respectively. XRD results confirmed that the growth process of ZnO involved a phase transformation from intermediate compound basic zinc carbonate to ZnO. Base on the experimental results, the formation mechanisms of two kinds of flower-like ZnO undergoing nucleation, oriented growth and self-assembly processes were discussed. The photocatalytic results indicated that both samples exhibited high photocatalytic activities and good cycling stability for the degradation of rhodamine B (RhB), which was almost completely degraded within 25 min, in comparison to those milled samples (above 45 min). The excellent performances were mainly ascribed to their unique nanostructure, good stability, and uniform particle size. (C) 2015 Elsevier Inc. All rights reserved.