A method for converting a KVM system comprising the steps of: (1) initializing a mouse device, at least two computer hosts, a keyboard, and at least two corresponding displaying device; (2) selecting which computer host and a corresponding displaying device are needed to be operated, then switching to the selected computer host and the corresponding displaying device by controlling a switch disposed on the mouse into a particular direction; (3) operating the selected computer host and the corresponding displaying device; (4) finishing the operation; (5) judging whether one of the computer hosts and another corresponding displaying device is needed to be operated, if yes, going to step (2), if no, going to next step; and (6) end.