Abstract: The state of free surface is one of the important factors which influence the blasting effect.Firstly，the major fissure and heel，and karsts cave and soft interlayer phenomenon existing in the free surface in the process of the on-site construction were introduced，and the free surface of different states blasting effect were analyzed.Then according to the different state free surface，the specific measures were put forward，and the field test bench blasting was done.The results showed it feasible to take different measures according to different free surface conditions.After blasting the blocks are uniform and the bedrocks and flying rocks generated were reduced.

Key words: Bench blasting, Blasting parameter design, Blasting effects, Free surface