The invention relates to a silicon device on an insulator and a preparation method thereof, which belong to the technical field of semiconductor devices. The silicon device on the insulator is prepared from a silicon wafer on a p-shaped insulator and comprises a p-shaped bottom silicon substrate, a buried oxygen layer, an N-shaped field effect transistor and a P-shaped field effect transistor which are formed in a top layer silicon film; the N-shaped field effect transistor and the P-shaped field effect transistor are respectively positioned in a tagma zone and respectively comprise drain electrodes, source electrodes, grid electrodes and body lead-out parts; and the tagma zone containing the N-shaped field effect transistor is electrically isolated from the tagma zone containing the P-shaped field effect transistor. The silicon device on the insulator can effectively inhibit the floating body effect, has symmetrical source electrodes without extra parasitic capacitance and can be compatible with the silicon process and the design of a main flow body to the maximum extent while retaining the advantage of an SOI circuit.