The invention discloses a preparation method for 
mordenite with a high Si / Al ratio and a small 
crystal particle, which comprises the following steps of: firstly, dissolving an Al source in 
sodium oxide solution; after an Si source is added, stirring and dispersing for certain time at 
room temperature and under strong magnetic force; mixing the Al source solution and the Si source solution which are evenly dispersed into glue at the 
room temperature; adding inorganic lamellar precursors, such as lamellar 
zeolite molecular sieves, lamellar 
silicate and the like to serve as 
seed crystal; after mixture is stirred and mixed evenly at the 
room temperature and under the strong magnetic force, transferring into a reaction 
crystallization kettle; at the temperature of 150-170DEG C, carrying out 
crystallization reaction for 0.5-3 days; and obtaining a 
solid product after common suction 
filtration, washing and 
drying. The synthesis method disclosed by the invention has the characteristics that expensive organic amine template is not used as structure-directing agent, and instead, the easily-obtained inorganic lamellar precursors with abundant source and low price are used as the 
seed crystal to directly synthesize a 
mordenite molecular sieve with the high Si / Al ratio. The prepared nanometer 
mordenite molecular sieve has the advantages of high degree of 
crystallinity and purity, controllable particle size and morphology, low cost and small environment 
pollution, and is convenient for industrially producing on a large scale.