The invention relates to a method for cutting off a temporary support of a continuous girder bridge by a wire saw. The method comprises the following steps of: 1, chiseling a first groove at each of four corners of the lower part of the temporary support; 2, mounting wire saw equipment and a cutting wire; 3, cutting off the section of the lower part of the temporary support to perforate; 4, stuffing a disc steel bar into a gap at the section of the cut-off lower part of the temporary support; 5, chiseling a second groove at each of four corners of the upper part of the temporary support; 6, mounting the wire saw equipment and the cutting wire; 7, cutting the section of the upper part of the temporary support to perforate; 8, dismantling the wire saw equipment and the cutting wire; 9, pushing out the whole separated temporary support by a jack; and 10, symmetrically cutting off the residual temporary supports according to the modes from the step 1 to the step 9. According to the invention, in a process of dismantling the temporary supports of the continuous girder bridge, an accident can be effectively avoided, and the dismantling speed of the temporary supports can be quickened.