The effect of different beryllium (Be) contents on the microstructure evolution and mechanical properties of as-cast Zr-3Al-chiBe alloys (chi = 0, 0.4, 0.6, and 0.8 wt.%) was evaluated. X-ray diffraction and microscopic analysis showed that significant microstructural changes were caused due to the trace amount of Be in the as-cast Zr-3Al-chiBe alloy. On one hand, with the Be increased gradually from 0 wt.% to 0.8 wt.%, the shape of prior-beta grains gradually transformed from inerratic planar crystallization to irregular arborization. On the other hand, it would have an obvious effect on grain refinement with Be added. The average grain sizes of the prior-beta and alpha (the average length) phases exceeded 1000 and 100 mum, respectively, in the as-cast Zr-3Al alloy. Dramatically, with the addition of 0.4 wt.% Be, the average grain sizes of the prior-beta and alpha phases were decreased by more than 80% and 50%, respectively. Moreover, the average size of grain decreased with increased Be. The enhancement in nucleation rate and the growth restriction factor values of Zr-3Al-chiBe alloys with Be addition were responsible for the refinement of the prior-beta and alpha grains. In addition, the tensile strength and hardness of Zr-3Al-chiBe alloys gradually increased with the increased Be content. The decrease in the alpha grain size and the presence of Be sub(2)Zr particles played identically important roles in improving the tensile strength and hardness of alloys.