In order to control the forming effect of excavation profile and reduce the disturbance of preserving rock mass caused by blasting,the foundation pit blasting at the Yunnan bank of the large arch bridge across Jinsha river,whose total depth is about 51 m and one-time excavation depth is about 20 m,is taken as the engineering background.Reinforced loose blasting with hole-by-hole initiation was applied to the main blasting holes and smooth blasting was used for the contour holes.A kind of deep hole smooth blasting technology which can be applied to foundation pit excavation of the deep and steep arch bridge is presented.In addition,the action process of gas,the expansion pressure at the hole wall and the damage range of the smooth blasting hole were theoretically calculated and analyzed.The blasting results show that a flat excavation profile,with more than 90% half-hole ratio of relatively intact rock mass and less reserved hole marks of relatively cracked rock mass whose overbreak and underbreak can still be controlled,can be formed by using the deep hole smooth blasting technology,which greatly reduces the stress concentration on the rock wall surface.The crushing zone will not be formed near the charge section in the smooth blasting and the maximum damage range of the reserved rock mass was about 49cm,which fully ensured the rock wall stability and construction safety.In the process of smooth blasting construction,engineering measures were also taken to ensure the reliability,safety and economy,including slowly tilting the excavation surface at the bottom of the bench to the free surface,tying the explosive charge with cotton rope for traction,and setting detonators inside and outside the hole every 5~7 smooth blast holes.