Incorporating with molecular dynamics method of two-temperature model, the effect of B2 structure Ni-Ti shape memory alloy film ablated by femto-second laser with 100 fs ultra-short pulse width is simulated in number and the phase transition of the target with lower energy density is researched. The results show that thermal energy relaxation is caused by the propagation of pressure wave when ultra-high speed laser interacts with B2 structure Ni-Ti shape memory alloy. The laser with 100 fs pulse width and 20~35 mJ/cm2 power density interacting with the target, the phase change of the target is induced by the pressure wave from ablating process during propagation. And a sandwich structure is formed.