A sulphonyl tetrazole compound 7 with the following structure, its preparation method and its use for preparing laetispicine. The said sulphonyl tetrazole compound 7, (1-phenyl-5-(3,4-methylenedioxyphenyl ethyl) sulphonyl tetrazole), is obtained from piperonal as raw material and by steps of Darzens condensation, hydrolysis, decarboxylation, reduction, condensation and oxidation. Laetispicine is prepared from the said compound as raw material, by condensation with 9-carbonyl-2E-4E-nonadienoic acid isobutyramide (compound 14), or by reaction with 5-(tetrahydropyran-2-oxo) n-pentanal (compound 10), deprotection, Swern oxidation, Wittig-Horner reaction, hydrolysis and amidation. As shown in H NMR, C NMR, MS and IR, the laetispicine prepared from the above-said compound is consistent with the laetispicine extracted from natural products.