A new method of deposition of an organosilicon thin film by magnetic-controlling plasma polymerization has been successfully used to protect a YBa2Cu3O7-delta (YBCO) superconductor from corrosion. The organosilicon (hexamethyldisilane-HMDS) protective film obtained is homogeneous, compact, pinhole free, and highly crosslinked. The deposition rate of the polymer film increases rapidly first and then decreases, as radio frequency input power and HMDS monomer pressure increase, respectively. The deposition rate of a plasma polymer film with magnetic controlling is 20 times higher than that without magnetic controlling. The YBCO superconductor covered with an organosilicon film by magnetic-controlling plasma polymerization has been protected from corrosion in water over 48 h.