Abstract: In the technological transformation of a thermal power plant，a new deaerator and some ancillary facilities with a total weight of 2 000 kN would be placed on two beams of Oxygen Room. The load far beyond the originally designed carrying capacity of beams. With analysis and appraisal，it was determined that they should be reinforced by method of section-steel bonded. Based on the theoretical assumption，positive bending moment reinforcement was designed by the classical theory of rectangular cross-section flexural strength，negative bending moment reinforcement designed by the formula form related experimental study. Processing and production of section-steel beams must be precise. As the deformation of section-steel beams was very difficult，so，the paste construction method offixed frist before perfusionshould be used，and to ensure the joint work of both old and new structures with the shear key plates，chemical anchorage and other structural measures were also used. After the construction，load-on field test was conducted，which showed that reinforcing effect was very good.