The invention relates to a safe span-crossing method for a double-guide-beam bridge girder erection machine. According to the method, two middle bridge deck longitudinal beams between a left outer side bridge deck longitudinal beam and a right outer side bridge deck longitudinal beam serve as anchoring balance weight beams for span-crossing of the double-guide-beam bridge girder erection machine;or one cross beam or two front and back adjacent cross beams are used as anchoring balance weight beams for crossing of the double-guide-beam type bridge; or two piers adjacent to each other left andright or two piers adjacent to each other front and back are used as anchoring balance weight beams for span crossing of the double-guide-beam type bridge. The safety and stability of span crossing ofthe double-guide-beam bridge girder erection machine are improved, and the method has the advantages of being simple, practical, small in mechanical and manpower investment, large in safety coefficient, capable of saving time and labor, high in construction efficiency, capable of saving cost and good in using effect.