Both variant type and structure characteristic of {10 1 2} twinning in the as-rolled AZ31 magnesium alloy subjected to dynamic plastic deformation at room temperature along the rolling direction were investigated. The results show that at the stage of twinning-dominated deformation (ε<8%), mostly a {10 1 2} twin variant or a twin variant pair is activated in the grain of AZ31 magnesium alloy, leading to a parallel twin lamellar structure. The lamellar thickness decreases significantly from 5.55μm to 2.49μm with increasing the strain. Meanwhile, different {10 1 2} variant pairs also generate in some grains, and the number of these grains increases with increasing the plastic strain. When the plastic strain is greater than 8%, the volume fraction of twins almost saturates and dislocation slips dominate the later deformation.%沿热轧退火态AZ31镁合金轧制方向进行室温动态塑性变形，采用场发射扫描电子显微镜研究{1012}孪生的变体类型及结构特征。结果表明：在{1012}孪生机制主导塑性变形的初级阶段(ε＜8%)，AZ31镁合金中大部分晶粒内部仅产生一种{1012}孪生变体或变体对，所以孪晶结构呈彼此平行状，将晶粒分割成片层组织；这种片层组织的厚度随着应变量的增加而减小，从5.55μm减小到2.49μm；少数晶粒形核产生不同的{1012}孪生变体，且这种晶粒的数量随着塑性变形量的增大而增加；当ε＞8%，孪生体积分数接近饱和，位错滑移成为镁合金主要的变形机制。
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