The invention relates to a monitoring system for a voltage critical condition of a power system and a construction method of the monitoring system. The construction method comprises the steps of monitoring and sending information such as voltages, currents, duration time and state warning of a power generator, a power plant and a power grid or requisition system state control information to an upper intelligent body by a distributed multi-intelligent body unit model configured at the power generator and a part of power transmission line, and receiving a control instruction; sending the information acquired by the distributed multi-intelligent body unit to an information collection integral analysis and control central station configured in a power system control center; judging whether thesystem is currently in an extreme critical state or a critical state or not by the information collection integral analysis and control central station according to the state warning or the requisition system state control information sent by each intelligent body; and if yes, forwarding to an artificial intelligent knowledge base for intelligent analysis and intelligent decision, issuing a system state control instruction by the distributed intelligent body according to a system state handling strategy built in advance, otherwise, ending analysis.