A blade driving mechanism for a table saw, wherein the table saw comprises a main frame and a saw blade mounted to an driven by the blade driving mechanism, and the blade driving mechanism comprises an electrical motor mounted to the main frame, with the motor being capable of sliding with respect to the main frame; a belt driving system for transferring the rotation of an output shaft of the motor to the saw blade; a center-distance setting device connected between the motor and the saw blade, for adjustably setting the center-to-center distance between the motor and the saw blade; and a saw-blade height adjusting device being operable to adjust the height of the saw blade.