加劲长悬臂板预应力混凝土箱梁桥在施工过程中，其节段线处悬臂板常常出现横向、斜向裂缝。为了制定合理措施来优化受力状态从而避免裂缝的出现，文中对裂缝的开展机理进行了研究，利用 MIDAS FEA 软件建立桥梁节段模型，进行自重和预应力作用下的剪力滞效应分析。通过将有限元计算结果与工程实测结果进行对比，验证了有限元模型的正确性; 通过改变预应力筋的张拉顺序，研究了不同工况下的截面应力状态，并用于指导工程实践。研究结果表明: 剪力滞效应造成的悬臂板端部压应力储备不足是导致悬臂端产生裂缝的原因之一，可通过悬臂端加配筋予以改善; 通过合理地改变预应力筋的张拉顺序，可以有效改善结构的预应力储备，优化应力状态，减少施工过程中裂缝的出现。

The prestressed concrete box girder bridge with long cantilever plates often has lateral and oblique cracks at the segmental junction during the construction process． In order to formulate reasonable measures to improve the cracks，the mechanism of crack development was studied． The bridge segment model was established by MIDAS FEA software and the shear lag effect under self-weight and pre-stress was analyzed． The finite element model was verified by comparing the finite element results with the measured values． By changing the tension sequence of the prestressed tendons，the stress state of the sections under different working conditions was studies． The results show that the insufficient compressive stress caused by shear lag effect at the end of the cantilever plate is one of the fac-tors contributed to the cracks at the cantilever end，and this can be improved by adding reinforcement at the canti-lever end． By reasonably changing the tension sequence of the prestressed tendons，the structural pretreatment and stress state can be effectively improved and the cracks during construction process can be reduced．