In this study, the quasi-hyperbolic approximation is used to investigate the dynamic behavior of a crack under the action of anti-plane stresses and in-plane electric displacements in a piezoelectric material. First, the steady-state response of a finite crack subjected to harmonically anti-plane loading and in-plane electric displacement on crack faces is analyzed. Moreover, a moving crack of Yoffe type in piezoelectric materials under remote anti-plane static stresses and in-plane static electric displacements is studied. The stress intensity factors and electric displacement intensity factors are obtained for both problems. Finally, numerical results of the first problem are evaluated and discussed in detail.