A lamp driving system controlled by electrical isolating is provided. The front-end power stage and the back-end power stage of the lamp driving system are electrically isolated each other by an electrical isolator. The lamp driving system includes a PFC controller for outputting a high voltage into a switching circuit. The switching circuit outputs a lamp driving voltage into the primary side of a boost transformer. A loading resonant network couples to the secondary side of the boost transformer, and generates a feedback signal. There are having the primary side of the electrical isolator, the PFC controller, the switching circuit and boost transformer coupled to a primary ground end. The PFC controller, the loading resonant network and the secondary side of the electrical isolator are coupled to a secondary ground end.