Based on the molecular dynamics method, the uniaxial tensile simulation of the bicrystal TiAl alloy containing voids is performed. The evolution behavior of defects and acoustic emission(AE) response on the deformation TiAl alloy and fracture of the TiAl alloy are studied at nanometer scale. The results show that the size and location of the voids have little influence on the elastic modulus of the TiAl alloy and the yield strength decreases with the increase of the void size. After plastic deformation, twin boundary can block dislocation emitted continuously at the edge of void, and increase crystal strength. When yield stress is reached, the TiAl alloy with voids at grain boundary is more likely to produce stable dislocation structure, which hinders the movement of other dislocations, thus improving the crystal strength. Through the analysis of the AE signals during the stretching process, it is found that the AE signals mainly come from lattice vibration, and has a large power range and a lower median frequency. The AE signals of dislocation slip reveal the characteristics of wide frequency domain, and the AE signals of dislocation proliferation and dislocation accumulation display the characteristics of low power. The AE signals of crack propagation belongs to the burst signal, which is characterized by high frequency and high power.