The paper discusses the omission in analyzing the worst stressed state and the mistake in strength and stability checking computations method for compression and bending member, by analyzing the available construction calculation analysis program function, in order to approach the reason of Qijiang arch bridge breakdown. Especially the paper queries whether there exists the bend section modular calculating method for dumbbell or round end rectangular section arch rib, to prove the existence of a lot of unsafe factors in the steel pipe-concrete arched bridge. Finally the paper recommends, the designer to change the idea of unilaterally chasing new and strange into the principle of safe, durable and useful,so as to design and build the structure that will never break down for a century.