The invention discloses a method for preparing metal-oxide-semiconductor field effect transistors (MOSFETs) with extremely short-gate length bulk-silicon surrounding gates, which comprises the following steps of: performing local oxidation of silicon isolation or trench isolation, depositing three layers of medium films which are a cushioning SiO2 oxide layer, SiN and an oxide medium layer respectively on bulk silicon, performing electron beam exposure, etching a groove and fin, depositing SiN sidewalls, isotropically etching Si, performing dry-oxygen oxidation, performing etching to remove the sidewalls on the two sides of the fin and simultaneously reserve the bottom sidewall of the groove, performing three steps of sacrificial oxidation to form nanowires, performing wet etching to reserve sufficiently thick bottom SiO2 for isolation at the same time of releasing the nanowires, depositing a gate medium and a gate material, performing two steps of source-drain injection after the gate is back-etched, depositing and etching the sidewalls, and forming contact. The method eliminates a self-heating effect and a floating body effect, is lower in cost, well compatible with a complementary metal oxide semiconductor process by completely adopting a conventional top-down process, and favorable for inhibiting a short channel effect and promoting the development of MOSFETs with smaller sizes, and easily realizes integration.