Based on 500 kV Lanxi substation smart modernization project of Zhejiang power grid， a series key modernization technologies and implementation programs for extra high voltage（EHV） smart substation are described， such as EHV substation equipment intelligent component， information integration platform， intelligent work sheet， AIS equipment one-button sequence control， intelligent alarm and fault comprehensive analysis， source maintenance， etc. The construction and operation experience of 500 kV Lanxi substation smart modernization project proves the effectiveness of the above mentioned key technologies.