The invention discloses a method for mounting overhead ground wire on horizontally-arranged 10KV insulated wire lines and a lightning arrester support, which can reduce the lighting striking rate of a wire, construction amount and operation cost. A ground wire support is fixed at a position, corresponding to the position of 1,780mm cross beam hardware of an original horizontally-arranged insulator wire line, on a line cement post. The ground wire support is comprised of a steel angle support and two sets of mounting loops; the up and down distance between the two sets of mounting loops is between 400 and 500 millimeters; one set of mounting loops are close to the upper side of the cross beam hardware, while the other set of mounting loops are positioned below the cross beam hardware; the distances between the mounting loops and the steel angle support are kept between 30 and 35 millimeters, so that the mounting loops cannot be overlapped with a cross beam round steel loop nor an inserting bolt; and the height of the steel angle support is kept between 1,90 and 2,000 millimeters, so that the lighting protection angle of a steel strand is between 29 and 33 degrees.