After a detailed analysis for the current situation of security protection in a hydropower station，the security architecture of power monitoring system in hydropower station is designed and proposed，which is strictly based on the " Information security technology － － Baseline for classified protection of cybersecurity" and " Ｒegulations on security protection of power monitoring system" and covers the technology and management together． The design also involves most subsystems of the station， and is feasible to be put into practice． Finally，several remaining issues which need to be improved are discussed in order to enhance the security architecture．