The invention discloses a small 
crystal particle Y-shaped 
molecular sieve and a preparation method thereof. The property of the small 
crystal particle Y-shaped 
molecular sieve is as follows: the 
molar ratio of Si, O2 / Al2O3 is 10.0-120.0, the 
cell parameters are 2.420-2.445 nm, the 
crystallization retention is larger than 95 percent, and B acid / L acid is above 7.0. Due to higher 
raw material thermal and hydrothermal stability, higher 
silicon-aluminum ratio, good stability and uniform framework 
silicon-aluminum structure, the small 
crystal particle NaY 
molecular sieve can ensure the framework continuity of the molecular 
sieve, reduce the collapse possibility of the framework structure and maximally keep the integrity of a 
silicon-aluminum-
oxygen structure in the modification, namely in the 
ammonia exchange, 
ammonium fluorosilicate dealumination and silicon reinsertion, hydro-
thermal treatment, aluminum salt and acid mixed water 
solution treatment process, thereby having high 
crystallization retention. The Y-shaped molecular 
sieve can be taken as an 
active component of a hydrocracking catalyst, thereby improving the activity of the catalyst, the selectivity of the molecular 
sieve and the product quality.