Key technologies of precision blasting were put forward based on characteristics of urban viaduct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamics model were established for quantitative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmentation. The initiation network of non-electric duplication crossover was adopted for safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Adverse effects were forecasted and controlled by integrated protective technologies. Specialization cooperation，precision，execution（SCPE）project management method was put forward for precision management. Key technologies of precision demolition blasting can provide reference for similar projects.