Stable and reliable observation environment is the basic requirement for high-quality observation data. The improvement of the observation environment of the stations has been received great attention by CEA in recent years. The Nationwide Key Seismic Stations Optimization and Reconstruction Project is committed to the optimization and transformation of the observation environment,infrastructure and working conditions of the seismic stations in order to adapt the requirement of the development of modern seismic observation technology. In this paper we systematically summarized the implementation of the Nationwide Key Seismic Station Optimization and Reconstruction Project from 2001 and analyzed the critical technologies. We mainly focused on the design of seismic instrument,non-magnetic technology of geomagnetic observation room,moisture-proof and thermal insulation of deformation cave,lightning protection transformation of overhead line of apparent resistivity observation,and station standardization transformation. Through these new technologies and processes,the observation environment is getting better,the quality of observation data is improved,and the high-quality basic data support is provided for earthquake monitoring,earthquake prediction and earthquake scientific research. Finally we discussed the new content and critical technology in the new situation to provide certain reference for the development direction of the station transformation in the future.