The reinforcement and construction of under origin arch is discussed in the paper.

Reinforcing skill of stone arch bridge by reinforced concrete arch-lifted method;

The application of grouting to consolidate foundation,combined with consolidating treatment of setting umbrella arch up and inverted arch down,has achieved good effect of engineering.

Combined with practical engineering,the author introduces the design and construction scheme of pilot pipes,and illustrates construction technology of large pilot pipes,trimmiog of operating platform,construction of umbrella arch,jacking of steel tube,and grouting of pilot pipes,in order to ensure safe and rapid implementation of construction.

Discussion of reinforced overspan stone bridge by cover-arch method;

According to the method of determining the safe thickness of arch ring which is reinforced by adding a new arch ring,this paper proposes a method for determining the thickness of inner arch ring under the arch bridge.