Based on the blasting demolition case of longitudinal concrete cofferdam of Wenzhai hydro-junction project, the project schedule, surrounding environment of blasting area and blasting scheme were studied in this paper, the cofferdam was successfully demolished by blasting with a combination of variable linear density charge and the initiation network of industrial electronic detonator.The cross section of the demolition body is narrow in the upper part and wide in the lower part.The fan-shaped arrangement vertical ultra-deep hole is drilled, and the variable linear density charge is adopted in the hole.In addition, the linear density length and linear charge density of each section are controlled by decreasing the loose blasting action index(n=0.4~0.6) and the powder factor(0.5~0.75 kg/m3).According to the protection requirements of the surrounding buildings and ecological environment, the maximum single blasting charge quantity is derived for demolition blasting.Through blasting monitoring, the harmful effects of blasting are controlled in safety.The quality of demolition body meets the design requirements.