The utility model discloses an auxiliary stay leg structure that is used for prefabricated segment roof beam to stride scaffold bridge crane one by one, include two landing legs arranging respectively at main frame both ends, call that a landing leg and no. Four landing legs respectively, landing leg includes the entablature, the roof beam of cranking arm, overcoat post, jacking cylinder, endotheca post, contact frame, adjustable brace and increase the festival, no. Four the landing leg includes overcoat post, jacking cylinder, endotheca post, bottom end rail and rail trucks. The utility model discloses the landing leg altitude mixture control of being convenient for adapts to different longitudinal slope's construction demand, avoids producing from the feeding beam operation of frame bridge crane afterbody fortune roof beam car and interferes to satisfy the construction demand of high -speed railway prefabricated segment roof beam.