Abstract: A new key technique system of highway hollow slab bridge widening alteration design constructing is proposed. It is realized by setting post-cast-strip between the new old cap beam, planting reinforcing steel bar on old border slab side face, and using steel fiber reinforced concrete in deck pavement. With this new technique, lengthways crack on the new old structure joint after constructing can be reduced. It is valuable for similar bridge widening alteration engineering.