Based on the construction of Baojiashan tunnel,the authors used numerical simulation and field test to analyze lining force,deformation and safety in the conditions of setting deformation joint and not. Studies suggest that:a. whether deformation joint is set or not,tunnel's vertical safety can meet the security requirements;b. if we do not set deformation joint for tunnel structure of the horizontal safety,the safety factor increases in V grade rock side,decreases in IV class rock side and reinforcement is needed at this time; when deformation joint is set,IV and V grade-level department of dome rock safety factors are smaller and can not meet the safety requirements,then reinforcement is needed.