Blasting engineering usually has great influence on adjacent buildings, for this edge load may cause some harm. Combining with characteristics of the blasting loads in blasting numerical simulation, the equivalent load was applied to the line of centers or the surface of blast hole in the same row to simulate explosion effect based on the Saint Venant’s principle, after making the blasting load applied to the blast hole wall equivalent by the equivalent applying method of the blasting load. Based on the equivalent load applying method, the three-dimensional entity model was used to calculate and analyse the effects of Donghai bridge in the far field of blasting construction on the stability of existing structures. The largest single explosive charge of different positions, different working conditions and different vibration response were calculated. Based on these results, the dangerous area of bridge structure was analyzed under the effects of the blasting edge load, the control of blasting quantity was put forward in different distances, which may serve as a reference for similar projects.