The utility model provides a but sliding scale's roof boarding support device, be fixed in including support frame and support the support fossil fragments of support frame top, an at least latch has been seted up to the support frame upper end, support fossil fragments bottoms be equipped with with the card foot that the latch corresponds, card foot buckle in in the latch and can slide in the latch. The utility model discloses but sliding scale's roof boarding support device, but sliding scale between support fossil fragments and the support frame can not produce temperature deformation and temperature stress's problem when meetting expend with heat and contract with cold to the roof boarding arch camber having avoided leading to because of temperature stress is too big, leak, life shortens the scheduling problem.