The invention discloses a dynamic capacity-increase full-cycle risk constraint and life evaluation method for local power grids. Through monitoring and early warning of thermal running parameters of key points of power transmission and transformation equipment in a capacity-increase full-cycle, closed-loop feedback of capacity-increase information and closed-loop correction of capacity-increase strategies, necessary on-site artificial special inspection monitoring and emergency intervention means are additionally adopted, dynamic capacity-increase running risks are reduced and controlled, load section obstruction problems caused by thermal stabilization are solved effectively to cope with N-1 and other running modes, and comprehensive running capabilities of power transmission and transformation equipment of local power grids or even of regional power grids are improved. Dynamic capacity-increase full-cycle running data is analyzed comprehensively, and running states and thermal life evaluation of power transmission and transformation (distribution) equipment are realized through a life evaluation analysis method.