Abstract: In the paper,the fatigue damage and breaking mechanism in wall rock in soft rock tunnel affected repeatedly by weaken blasting stress wave at distant place is firstly analyzed,then,the following conclusions that the change of mechanics capability of rock caused by fatigue damage that is produced by periodical load will play a important effect on long-term stability of rock engineering;there is a threshold of change for fatigue damage of rock,and,only when local strain of fatigue damage cumulates and achieves the above-mentioned threshold,the fatigue crack will come into being and expend;at the same time,because raising breaking toughness is less that breaking toughness for fatigue crack of rock,so,fatigue damage and breaking of rock affected by cycle stress that is less than break toughness will be caused are drawn.