The invention discloses a synthetic method of a beta molecular sieve. The synthetic method comprises the following steps: stirring a mixed alkali metal oxide source, an aluminum oxide source, a silicon dioxide source and water to synthesize initial gel; adding an organic template into the initial gel to obtain a mixture, stirring the mixture until the mixture is uniform, filling the mixture into a reaction kettle, and crystallizing for 48-100 hours at a temperature of 130-170 DEG C to obtain the beta molecular sieve, wherein molar ratios of various raw materials for preparing the initial gel are as follows: SiO2/Al2O3=28.8-55, Na2O/SiO2=0.04-0.24, H2O/SiO2=4-7, and the organic template/SiO2 =0.08-0.15; based on 100% of the mass of Al2O3, the aluminum oxide source contains 50%-100% of aluminum phosphite, wherein 0-50% of the aluminum oxide source is selected from one or more of sodium metaaluminate, pseudo-boehmite and alumina sol. The synthesized beta zeolite has a certain stacking holes for filtering easily and has good catalytic performances.