In this paper, the metastable β TB8 titanium alloy with nanocrystalline α phase is achieved by electric pulse treatment. The morphology evolution and variant selection of nanocrystalline α phase in metastable β TB8 titanium alloy were investigated by using scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) analysis. The results indicated that the morphologies of the nanocrystalline α phase were mainly triangular clusters and needle-like at the pressure of 0 MPa. With increasing pressure from 20 to 50 MPa, the volume fraction of needle-like α phase decreased, and a large amount of V-shaped α phase formed in the interior of β grains. Based on the EBSD data, the parent β phase was reconstructed by MTEX software. In the interior of the β grains, 12 variants can form for the samples electric pulse treated at 0 and 20 MPa, while only 3 and 6 variants can form for the samples electric pulse treated at 30 and 50 MPa. In the grain boundary of the β grains, one or more grain boundary α variants can be generated for the samples electric pulse treated at different pressures as long as one of the neighbor β grains follows the Burgers orientation relationship.Graphical abstract