The present invention discloses a manufacturing method of SOI MOS device having a source/body ohmic contact. The manufacturing method comprises steps of: firstly creating a gate region, then performing high dose source and drain light doping to form the lightly doped N-type source region and lightly doped N-type drain region; forming an insulation spacer surrounding the gate region; performing large tilt heavily-doped P ion implantation in an inclined direction via a mask with an opening at the position of the N type Si source region and implanting P ions into the space between the N type Si source region and the N type drain region to form a heavily-doped P-type region; finally forming a metal layer on the N type Si source region, then allowing the reaction between the metal layer and the remained Si material underneath to form silicide by heat treatment. In the device prepared by the method of the present invention, an ohmic contact is formed between the silicide and the heavily-doped P-type region nearby in order to release the holes accumulated in body region of the SOI MOS device and eliminate floating body effects thereof. Besides, the device of the present invention also has following advantages, such as limited chip area, simplified fabricating process and great compatibility with traditional CMOS technology.