The study on dynamic characteristics and windresistance performance of concrete encasement stage of arch bridge with stiff skeleton has great guidance for its construction. Tian'e Longtan Bridge serves as the research model here. With the aid of FEM software MIDAS/Civil, threedimensional finite element models of Tian'e Longtan Bridge are set up. Then, the change laws of natural frequency and wind resistance performance of the bridge in different construction stages under three different working platform conditions is investigated. The results show that the lateral frequency of the bridge shows a monotonically upward trend in the process of encasing concrete, while the vertical frequency is decreased first and then increased, and the phenomenon of veering will occur. the wind resistance performance is increased first, then decreased and finally increased again. The wind resistance is also affected by the number of working platforms. The more working platform there are, the weaker the lateral wind resistance of the structure.