The invention discloses a synthesizing method of a high-dispersion submicron ZSM-5 zeolite molecular sieve. By means of the method adding pre-crystallization liquid in crystallization mother liquid and segmentally adding alkaline in the hydro-thermal synthesis process, the ZSM-5 zeolite molecular sieve with particles mainly concentrated to be 400-500nm is obtained by synthesis and has good industrialized application prospect. The synthesizing method mainly solves the problem that the ZSM-5 zeolite molecular sieve synthesized in an existing template-free method causes large particles to be gathered easily, and the synthesizing method reduces synthesizing cost of the ZSM-5 zeolite molecular sieve in comparison with an organic template method. The synthesized ZSM-5 zeolite molecular sieve does not need roasting, and can manufacture various catalysts by modification such as ion exchange.