HZSM-5 molecular sieve, preparation method thereof and application of HZSM-5 molecular sieve in light hydrocarbon catalytic cracking

The invention provides a preparation method of an HZSM-5 molecular sieve, which comprises the following steps: S) mixing a first organic template agent, alcohol, water, an aluminum source, a first silicon source and an all-silicon seed crystal, carrying out hydrothermal crystallization, and roasting to obtain the HZSM-5 molecular sieve, the first organic template agent is an organic amine compound; the alcohol is C3 or more than C3 alcohol. Compared with the prior art, in the alkaline system containing the silicon source, the aluminum source, the organic template agent and the water, by adding the special seed crystal and the organic auxiliary agent, the length of the b axis and the c axis of the HZSM-5 molecular sieve can be regulated and controlled in the crystallization process; the molecular sieve catalyst modified by P and/or metal has high ethylene and propylene yield in the catalytic cracking reaction of C4-C8 and other light hydrocarbon raw materials with isoparaffin and cycloparaffin as main componen