ZSM-5 zeolite was successfully synthesized in an organic template-free system by a dry gel conversion (DGC) method. The influence factors, such as crystallization temperature, crystallization time, water content in the autoclave and the SiO2/Al2O3 molar ratio in the dry gel, have been investigated systematically. A series of DGC-ZSM-5 zeolites were characterized by XRD, SEM, XRF, BET and NH3-TPD. The results showed that the high crystallinity of ZSM-5 could be obtained without organic template. The content of water in the autoclave and the SiO2/Al2O3 molar ratio have a significant effect on the crystallinity and purity of DGC-ZSM-5. Furthermore, a possible formation mechanism was proposed based on the investigation of the crystallization process. Compared with the zeolite synthesized by hydrothermal method, the DGC-ZSM-5 zeolite not only exhibits much shorter crystallization time and smaller particle size, but also retains the synthesis gel SiO2/Al2O3 molar ratio in the final materials.