The tensile deformation and fracture behavior of the Ti555211 alloy were investigated using in-situ SEM technology. Results showed that it was found that slip bands were given priority within the lamellar structure with the tensile loading direction for the Ti555211 alloy with initial lamellar structure. As the crack propagated, the slip bands appeared dense. Moreover, for the alloy with initial lamellar structure, the crack propagated from the corners of the indention both across and along the lamellar directions.The Ti555211 alloy with initial lamellar structure show different fracture morphologies. For the alloy with initial lamellar structure, visible shear lips and a number of dimples were observed in fracture. The deformation and fracture behavior of the near-β titanium alloy of Ti555211 can be tracked by the SEM in-situ tensile test method in real time. The results of this method are more scientific and informative.