The invention discloses a multifunctional device guaranteeing computer data security. The device comprises a PCI card (2) installed in a computer mainframe (1), a nine-pin D-sub connector (3) connected with a socket data line, a standard five-hole plug group (8) arranged on a socket main body (5), a three-pin plug (7) connected through a wire (6), a slot (9) where an SIM for remote data communication is inserted, and a self-reset switch (10), wherein a slot for the PCI card is an international standard computer expansion card and is provided with a nine-pin D-sub interface; and the nine-pin D-sub connector (3) is connected with the socket main body (5) through a data line (4). The multifunctional device guaranteeing computer data security enables a computer to enter a dormant state, and a computer external power supply can be cut off, so that the computer data security is guaranteed.