The threshold control of safety blasting vibration velocity is a significant process for the underground mining of complicated ore deposit under construction, road, and water. According to the equivalent principle of displacement and velocity of mass point, differential evolution is put forward based on 3DEC dynamic analysis, making the calculation more efficient and accurate. The 3DEC model of the complicated orebody under railway is established according to the topographic maps and geological data of the eastern Pyrite Mine. The stimulus-response distribution of internal stress and displacement fields are demonstrated by analyzing the on-site monitoring vibration displacement and velocity data of the mass point. The reliability of parameter selection, such as blasting simulation waveforms, rock damping, is identified. The safety vibration velocity of railway is set to 4.5 cm/s in line with the requirement of safety blasting rules. Thus, the maximum amount of single-stage explosive in this region is 44.978 kg. The simulation result is in good agreement with the on-site monitoring datum. No displacement and settlement of the 701 railway special line was achieved by choosing the critical amount of the singlestage explosive.