To study the stress distribution law of the concrete saddle in pylon of extradosed bridge and to optimize the reinforcement layout for the saddle , the Ningjiang Songhua River Bridge was cited as an example and was analyzed .By means of the MIDAS Civil ,the spatial link model for the w hole bridge of the bridge w as established and the global mechanical behavior of the bridge was analyzed .Further by means of the ABAQUS ,the solid element models for the pylon and saddle were established and the numerical analysis of the saddle was conducted ,respectively using the extended finite element method and the concrete plastic damage constitutive model .The results of the analysis demonstrate that ① under the action of the stay cable forces ,the concrete saddle of the extradosed bridge may produce splitting cracks through the stay cable ducts and it is proposed the diameters of the reinforcement for the saddle should be enlarged or the spacing dis‐tances of the horizontal reinforcement should be densified;② under the action of the stay cable forces ,at the abrupt junction of the saddle structure ,the stress concentration may occur ,the principal compressive stress values will exceed the standard values of compressive strength of the C50 concrete and it is proposed that the rounded corner or the round corner at the junction should be added and ③ the extended finite element method can be used to well predict the occurrence and propagation of the cracks ,the prediction results of the method are basically agreeable with the re‐sults of the concrete nonlinearity analysis method ,how ever ,as regards the stress field calculation for the cracks ,there exist some differences between the two methods .%为研究部分斜拉桥混凝土索鞍的应力分布规律、优化索鞍的钢筋配置，以宁江松花江特大桥为背景进行分析。采用MIDAS Civil建立全桥空间杆系模型分析桥梁整体受力特性，再基于ABAQUS建立索塔及索鞍实体单元模型，分别采用扩展有限元方法和混凝土塑性损伤本构模型对混凝土索鞍进行数值分析。结果表明：①部分斜拉桥混凝土索鞍在斜拉索索力作用下将产生贯穿孔道的劈裂裂缝；建议增大钢筋直径或者加密水平钢筋间距；②在斜拉索作用下索鞍结构外形突变处产生应力集中，主压应力值超过C50混凝土的抗压强度标准值，建议增设倒角或者圆角；③扩展有限元方法可以较好地预测裂缝的发生与扩展，与混凝土非线性分析的结果基本一致，但在裂缝处的应力场计算有所差异。
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