How the plasticity features influence the fracture behaviors of material is a critical question but remains far from well understood. To disclose this mystery, a multiscale plasticity-fracture coupled model is developed, which considers the atomistic-scale dislocation motion mechanism, the mesoscopic scales of discrete crack-dislocation interactions, and the continuum scale of crystalline plastic-fracture response. Body center cubic (bcc) material is chosen as an example to demonstrate the effectiveness of the developed model due to their wide applications and their speical plasticity feactures, such as strong temperature dependence and non-Schmid effect. Several new insights about the fracture behavior of bcc material are gained.