Nano-sized ZSM-5 aggregates are widely used in preparing catalyst because of the higher reactivity and hydrother-mal stability.The nano-sized ZSM-5 aggregates with low Si/Al ratio were prepared by hydrothermal synthesis using sodium silicate as silica source,aluminum sulfate as aluminum source and n-butylamine as template.The effect of Na₂O/SiO₂ ratio,aging time and seed addition amount on the morphology and grain size of the synthesized zeolite were investigated.The sample was analyzed by the means of powder X-ray diffraction,scanning-electron microscopy,N₂ adsorption and desorption,trans-mission electron microscopy and X-ray fluorescence.The results showed that zeolites with good crystallinity can be synthe-sized at the amount-of-substance of Na₂O/SiO₂ greater than 0.11,however,when the n（Na₂O）/n（SiO₂）>0.13,the zeolite crys-tal size increased.In addition,when the aging time extended,the zeolites crystal particle and uniformity increased,and the average crystal size was approximately 160 nm at aging time of 12 h.There was nearly no effect of seed addition amount（3%~4%） on the crystal size and uniformity of the sample.