Herein, we develop a reproducible in situ crystallization route to synthesize uniform functional ZSM-5 microspheres composed of aggregated ZSM-5 nanorods and well-dispersed uniform Fe3O4 nanoparticles (NPs). The growth of such unique microspheres undergoes a NP-assisted recrystallization process from surface to core. The obtained magnetic ZSM-5 microspheres possess a uniform size (6-9 mu m), ultrafine uniform Fe3O4 NPs (similar to 10 nm), good structural stability, high surface area (340 m(2)/g), and large magnetization (similar to 8.6 emu/g) and exhibit a potential application in Fischer-Tropsch synthesis.