At present, retrofit of public buildings on energy effi ciency in China has achieved gratifying results, yet there are problems to be solved. This paper, based on investigations, examines problems existed during retrofi ts in metropolis and then demonstrates the importance and significance of controlling thermal comfort standards as well as adopting compositive energy-efficient technologies based on energy diagnosis. The paper takes a retrofit project in an university of Xi’an as an example, points out properties operating characteristic of architecture, advocating that detailed analysis on climate conditions and utilization patterns of target buildings are essential to set reasonable thermal comfort standards; energy diagnosis should also be paid attention to identify the potentials for energy conservation.