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为了进一步理解机械应力对交联聚乙烯(XLPE)电缆中水树生长的影响，研究了机械应力和XLPE样本中水树形态之间的关系，并提出了XLPE材料的力学取向对水树生长的作用机制。以热钢针在两组XLPE样本中扎孔的方式模拟电缆绝缘受到的机械应力作用，并仅对其中一组样本进行加速水树老化实验，另一组样本仅利用偏光显微镜观察针孔缺陷周围的应力纹形态(XLPE 材料取向的宏观形态)。在水树老化样本中发现了异常水树形态，而此异常水树形态和未进行水树老化的样本中观察到的应力纹形态极其相似。以高分子力学取向理论为基础，并结合电场仿真模型，分析了XLPE材料的力学取向和水树形态的内在联系。研究表明， XLPE 材料的力学取向在很大程度上决定了水树的生长方向。由于XLPE材料取向后出现各向异性，在取向方向上水树生长将得到促进，而在与取向方向垂直的方向上水树生长将受到抑制，从而导致异常水树形态的出现。“,”To further understand the effect of mechanical stress on water tree propagation in XLPE cables, in this paper, the correlation between mechanical stress and water-tree morphologies in XLPE samples is studied, and the mechanism of mechanical orientation of XLPE materials on water tree propagation is proposed. The mechanical stress was simulated by inserting a heated syringe needle into two groups of XLPE samples, and only one group of samples were subjected to an accelerated water tree aging experiment, the other group of samples were only observed for stress strips (the macroscopic morphologies of orientated XLPE materials) using a polarizing microscope. In water tree aged samples, abnormal water-tree morphologies were found, which were very similar to those of stress strips in the other group of samples. Based on the mechanical orientation theory in polymer physics, combining with electric field simulation model, the internal relations between the mechanical orientation of XLPE materials and water-tree morphologies were analyzed. The results indicate that the mechanical orientation of XLPE materials plays a leading role in the propagation direction of water trees to a large extent. Since anisotropy emerges in oriented XLPE materials, in orientation direction, the propagation of water trees is promoted, while in the direction perpendicular to the orientation direction, the propagation of water trees is inhibited, thus resulting in the formation of abnormal water-tree morphologies.