β-isophorone was obtained from α-isophorone via isomerization, which was then reacted with trimethylchlorosilane using sodium iodide as the catalyst to get β-isophorone trimethylsilyl enol ether. After Aldol reaction with crotonaldehyde, the important Tobacco fragrant component Megstigmatrienone was synthesized. The structure of the product was identified by GC-MS. The Overall yield was 35%, the content was 75%.