The invention relates to a method of synthesizing Beta molecular sieve without organic templates, which belongs to the technical field of catalytic chemistry. The steps of the invention comprise mixing alkali oxide sources, alumina sources, silica sources and water, stirring and synthesizing initial silica-alumina gel, then adding with Beta zeolite crystal seed, crystallizing 12-24 hours under the temperature of 100-180 DEG C and hydro-thermally synthesizing the Beta molecular sieve, SiO2/Al2O3 of the Beta zeolite crystal seed equals 22-25, and the quality of addition quantity is 5%-20% of the silica sources. The method of the invention suits requirements of applying zeolite molecular sieve in industry, not only can directly synthesize high crystallinity crystal of the Beta molecular, but also can increase crystallizing speed of the molecular and reduce manufacturing cost. Because the synthesis process doesn't use any organic templates without roasting, thereby a pore path is unimpeded, and environmental pollution and relatively consumption are avoided.