A synthetic method of Nanosized ZSM-23 zeolites belongs to the technical field of synthesis of inorganic chemistry. Firstly preparing reaction mixture from sodium metaaluminate or aluminum sulfate, silicasol or soluble glass, sodium hydroxide and isopropylamine, then hydrothermal crystallizing the reaction mixture, at last obtaining the Nanosized ZSM-23 zeolites through conventionally filtering, washing, drying and sintering the hydrothermal crystallized reaction mixture. The synthetic method has the advantages that average diameter of the cross sections of crystal grains of the synthesized ZSM-23 zeolites is not more than 100 nm, the specific surface area is comparatively high, production flow is short, the cost is low, and the method is favorable for industrial production and application.