No-load　noise,　mainly　comes　from　the　magnetostriction　of　the　grain-oriented　silicon　steel,　is　one　of　the　main　noise　sources　of　transformers.　The　noise　level　can　be　amplified　when　natural　frequencies　of　the　core　get　close　to　the　frequency　of　magnetostriction.　Therefore,　modelling　the　stacked　grain-oriented　(GRO)　silicon　steel　is　valuable　for　designing　low-noise　transformers.　This　paper　firstly　conducts　vibration　tests　of　silicon　steel　sheets　to　obtain　the　variation　law　of　the　natural　frequency　of　stacked　silicon　steel　sheets.　Secondly,　an　equivalent　method　is　proposed　to　establish　the　transversely　isotropic　model　of　the　stacked　iron　core.　Then,　the　influence　of　such　as　the　length　of　the　yoke,　the　height　of　the　core　column　and　the　thickness　of　the　core　on　the　natural　frequencies　are　discussed.　Lastly,　an　appropriate　size　range　of　the　core　to　avoid　noise　amplification　is　obtained.　The　conclusion　provides　the　basis　for　the　optimal　design　of　the　low-noise　transformer.