Due to the limitation of the size of the site, the demolition blasting of the tall chimney needs to be collapsed.In order to further study the optimal delayed initiation time of the upper and lower blasting cuts in the two-way folding directional dumping blasting demolition of a 100 m reinforced concrete chimney in a complex environment, a common node separation model is established with LS-DYNA and Hypermesh, and the steel joints and concrete joints are directly produced as unit bodies.At the same time, the numerical simulation results are compared and analyzed with the actual project.Through the simulation analysis of the collapse process and results under different delay time of the upper and lower cuts of the chimney, 1 s, 1.5 s, 2 s, 2.5 s and 3 s, the collapse degree of the chimney, and the explosion range and after analyzing and comparing the speed of chimney touching the ground, it is determined that the optimal delay time of the upper and lower cuts is 2.5 s.The result of numerical simulation calculation is highly consistent with the actual project.