After the impoundment of the LD Hydropower Station, the dam crest deformation of its powerhouse dam section continued to increase, and the maximum deformation exceeded the original calculated value. In view of this situation, a finite element software is used for the simulation calculation of the section from three aspects, namely, external load component, temperature component and aging component. The reason for the continuous increase of dam crest deformation is analyzed by comparing the superimposed deformation with the measured deformation. The calculation results show that the external load component accounted for the largest proportion of the dam crest deformation, which was 50% of the total deformation, followed by the aging component and temperature component, accounting for 27% and 23% of the total deformation respectively. After the water level in front of the dam reached the stable state, the deformation increment of the dam crest was mainly caused by aging and temperature, of which aging deformation accounted for 86% and temperature deformation accounted for 14%. With the passage of time, the concrete creep gradually converged, the temperature field gradually stabilized, and the aging deformation and temperature deformation tended to stabilize as well. Therefore, the dam crest deformation did not continue to increase. The original deformation calculation method did not consider the influence of temperature and aging, resulting in the monitoring value being greater than the original calculated value. It is suggested that the influence of temperature and aging on structural deformation should be fully considered in the deformation calculation of similar projects. The research results can provide a reference for the deformation review and prediction of the powerhouse dam section of riverbed hydropower stations, and provide a new idea for solving similar engineering problems.