Box girder bridges have good integrity and stability. For old bridge with T-section design that has inadequate bearing capacity, this paper suggests changing T section into box section to reinforce and upgrade the overall bearing capacity of bridge. Via finite element modeling analysis, this paper compares bridge stiffness, load distribution and span section bending bearing capacity upgrading, etc. , before and after reinforcement, to study the feasibility of this reinforcing method in similar old bridge reinforcement.%箱形截面梁桥具有良好的整体性和稳定性。对于原设计T形截面局部T梁承载能力不足的旧桥，提出采用原截面转换成箱形截面的方法对其进行加固，以提升桥梁整体承载能力。通过有限元建模分析，对加固前后桥梁刚度、活载分布以及跨中截面抗弯承载力提升等进行比较，研究该加固方法在此类旧桥加固中实施的可行性。
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